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.-« •• 

• • • 

'• . «• 
















■ntn N fcm;ndation8. 



Copyright, nM)7, by Intkrkationai. Thxtbook Company 

Entcrctl at Stationens' Hall. London. 


CarburetCBB:. ^Cfjpyrijiht, 1UU7, by Intkrnational Tkxthqok Company. Entcro 
at Statifrsci;?'^ Uall, ^"nd^n * • - ^ . » , 

Electric rKtlition 'DtviCes: "Goifiyrii^; a907, by International Textbook Com 
PANY. Ente^iwl a^ SUitjgners' Kail, ""London. 

Automobile and^ Mj^i*^ A^^ncf '^pxiliaries: Copyright, 1907, by Inteknationai. 
TEXTHOOi^CoMpAhT?.* Swfe»5d aft Stationers' Hall, I.K)n(l()n, 

Power-Gas PiYdi«;0^;*"^ (jnpiCrf^, MK)7, by International Textbook C(^mpanv. 
Entered at ^tal vid^' >IkK* Xc^ndt^ . 


Manaf[ement of Automobile Engines: Copyright. 1907, >)y International Text- 
book Company. Entered at Stationers' Hall, I.xmdon. 

Management of Marine Gas Engines: Copyright, 1U07, by Intp.knatidnal Text- 
book Company. Enterwl at Stationers' Ilall, Lomlon. 

Management of Stationary Oas Engines: Copyright, 11)07, by International Text 
book Company. Entere<J at Stationers' Hall, London. 

Troubles and Remedies: Copyright. HK)7, by International Textbook Com- 
pany. Entered at Stationers' Hall, London. 

Power Determinations: Copyright, 1907. by Intkrnational Textbook Cdmi'anv. 
Entere<l at Stationers' Hall, London. 

All rights reservcil. 



^'■■7 .".■■?*."iA 





The International Library of Technology is the outgrowth 
of a large and increasing demand that has arisen for the 
Reference Libraries of the International Correspondence 
Schools on the part of those who are not students of the 
Schools. As the volumes composing this Library are all 
printed from the same plates used in printing the Reference 
Libraries above mentioned, a few' woMs dre iiecessary 
regarding the scope and purpose of' the instruction imparted 
to the students of — and the class of stuUelits taught by — 
these Schools, in order to afford a clear understanding of 
their salient and uhique features. ' ' * *' •■ 

The only requirement for admission to any of the courses 
offered by the International Correspondence Schools, is that 
the applicant shall be able to read the English language and 
to write it sufficiently well to make his written answers to 
the questions asked him intelligible. Each course is com- 
plete in itself, and no textbooks are required other than 
those prepared by the Schools for the particular course 
selected. The students themselves are from every class, 
trade, and profession and from every country; they are, 
almost without exception, busily engaged in some vocation, 
and can spare but little time for study, and that usually 
outside of their regular working hours. The information 
desired is such as can be immediately applied in practice, so 
that the student may be enabled to exchange his present 
vocation for a more congenial one, or to rise to a higher level 
in the one he now pursues. Furthermore, he wishes to 
obtain a good working knowledge of the subjects treated in 
the shortest time and in the most direct manner possible. 

• • • 



In nicctinc: these requirements, we have produced a set of 
books that in many respects, and particularly in the general 
plim followed, i'lre absolutely unique. In the majority of 
Miil)jei'ts treated the knowledge of mathematics required is 
limiti»<I to the simplest principles of arithmetic and mensu- 
ration, and in no case is any greater knowledge of mathe- 
tuaticH needed than the simplest elementary principles of 
al^obra, geometry, and trigonometry, with a thorough, 
practical aaiuaintance with the use of the logarithmic table. 
To otToct this result, derivations of rules and formulas are 
omittoili but thorough and complete instructions are given 
tv^iU'ding how» when, and under what circumstances any 
particular rule, fonnula. or process should be applied; and 
whotu^vor possible one or more examples, such as would be 
hkc^v U^ arise in actual practice — together with their solu- 
tiotitiC ^icri" ^.rvVn'.ijj rthi5tr*jto and explain its application. 

lu piV4MnA>: titost^.tcxibooks, it has been our constant 

env5ca\KV\^^ VjiwXTlfu:- matter from the student's standpoint, 

^ttut :*5 i;^\i;Vvr'tt:a"cipatc ovorvthing that would cause him 

*/•"•**"•*«« • 
t'v.iV'c *'T^^ V?;Vt^5t iwins have been taken to avoid and 

vvvv: .riY Av.vt alVa:*.tbij:uous expressions — both those due 

:o :,i;'.':v :>.o:v^r:c ,;!:v: :hv>so vh:e to ir.sufnciency of sraietnent 

sV ov.i\^**^' * ^^> *-^" *^^>' ^^-^y *-^ r::.ike a statement, 

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, VV • . » X » •» ■• X X X-.X...> V. «..* a^^... .^^wi, ^» \.»^ CV 

X ^- X>« x^ IX -vv -. ,.>xN. .-,x ^ ,> •'...^_ -v -._. w^:>l 

^ *,^ V, -x^ x» x^- .^ .... ^. --^ .^^w— _ •. ^w \m 

..■». . ..• »xx »• • ■«..^. ■.'^•"■x"", "■-■ "^J "•■J ;"ii— ".c— -* 

X ^^«. _ xX.*x .^xx«.:~x^ ■.^». >_ ^ ^ w «- ^ _ mAu^ 

*• X X ■ "i " X X. ■ ■x.x """"** ■"■■■" - JX.*" 

:-r'i i-e 


indexes are so full and complete, that it can at once be 
made available to the reader. The numerous examples and 
explanatory remarks, together with the absence of long: 
demonstrations and abstruse mathematical calculations, are 
of great assistance in helping one select the proper for- 
mula, method, or process and in teaching him how and 
when it should be used.' 

In the first two sections of this volume are described 
carbureters and electric-ignition devices used in automobile, 
marine, and stationary gas engines. In the third section are 
described transmission gears, differentials, clutches, revers- 
ing gears, etc. Under power-gas producers are treated the 
construction and operation of generators and of the purify- 
ing devices used in connection with producer plants, as 
well as cleaning devices employed with blast-furnace gas. 
In the next three sections are treated the management of 
automobile, marine, and stationary gas engines, including 
their installation, starting, stopping, and c^re. Under the 
head of troubles and remedies are considered the various 
troubles encountered in the operation of gas engines, 
together with their causes and remedies. In the section on 
power determinations are taken up the methods of deter- 
mining the power of an engine by means of the indicator, 
the brake, or by approximate formulas. The entire volume 
is exceedingly practical and valuable to all interested in gas 

The method of numbering the pages, cuts, articles, etc. is 
such that each subject or part, when the subject is divided 
into two or more parts, is complete in itself; hence, in order 
to make the index intelligible, it was necessary to give each 
subject or part a number. This number is placed at the top 
of each page, on the headline, opposite the page number; 
and to distinguish it from the page number it is preceded by 
the printer's section mark (§). Consequently, a reference 
such as § 16, page 26, will be readily found by looking along 
the inside edges of the headlines until §16 is found, and 
then through §16 until page 26 is found. 

International Textbook Company 

• 4 


Carbureters Section Page 

Gaseous Mixtures for Gas Engines ... 17 1 

Explosion of Gases 17 1 

Gas and Air Mixing 17 10 

Carburization 17 14 

Types of Carbureters 17 15 

Stationary-Engine Carbureters 17 19 

Automobile and Marine Engine Carbu- 
reters 17 27 

Carbureter Adjustment 17 45 

Electric Ignition Devices 

Make-and-Break Ignition 18 1 

Jump-Spark Ignition 18 7 

Primary Batteries 18 10 

Care of Primary Batteries 18 11 

Secondary, or Storage, Batteries 18 13 

Care of Storage Batteries 18 14 

Construction and Operation of Spark Coils 18 24 

Care of Spark Coils 18 29 

Types of Spark Plugs 18 31 

Auxiliary Spark Gap 18 35 

Construction and Operation of Timers . . 18 37 

Construction and Operation of Distributors 18 41 

Ignition Generators 18 45 

Magnetos 18 48 

Care of Dynamos and Magnetos 18 59 

Switches 18 60 

Make-and-Break Wiring 18 65 

•• • 


Electric Ignition Devices — Continued Section Paj^e 

Jump-Spark Wiring 18 68 

Ignition Wire Cable 18 69 

Automobile and Marine Engine Auxiliaries 

Speed-Changing Systems 19 1 

Sliding-Gear Transmission System ... 19 2 

Individual-Clutch Transmission System . 19 7 

Planetary Transmission System ..... 19 10 

Reversing Gears 19 12 

Principles of Operation of Differential 

Gears 19 15 

Spur-Gear Differential 19 15 

Bevel-Gear Differential 19 16 

Couplings 19 17 

Clutches 19 19 

Brakes 19 23 

Hand Starter for Automobiles 19 24 

Automatic Starters for Automobiles ... 19 25 

Marine-Engine Starters 19 26 

Automobile Governors 19 28 

Marine-Engine Governors 19 32 

Marine-Engine Water-Cooling System . . 19 33 

Automobile-Engine Water-Cooling System 19 34 

Radiators 19 37 

Circulating Pumps 19 39 

Mufflers 19 42 

Screw Propellers 19 45 

Power-Gas Producers 

Classification of Producers 20 1 

Pressure Gas Producers 20 4 

Suction Gas Producers 20 6 

Large-Capacity Producer 20 11 

Combined Producer and Evaporator ... 20 13 

Down-Draft Producer 20 16 

Preparing Producers for Operation .... 20 19 

Lining the Producer 20 20 

Filling the Scrubber 20 22 


Power-Gas Producers — Continued Section Page 

Pipe Connections 20 23 

Testing for Leaks 20 24 

Starting the Producer 20 25 

Firing the Producer 20 27 

Stopping the Producer Plant 20 28 

Restarting the Producer 20 29 

Cleaning the Pipe Connections 20 29 

Operation of Pressure Producers .... 20 30 

Blast-Furnace Gas for Gas Engines ... 20 31 

Cleaning Blast-Furnace Gas 20 33 

Management of Automobile Engines 

Inspection, and Location of Faults ... 21 1 

Care of the Engines 21 12 

Starting and Stopping 21 15 

Timing the Valves 21 17 

Retiming the Ignition 21 19 

Replacing Exhaust- Valve Keys 21 20 

Making Valve-Stem Keys 21 21 

Taking Off and Replacing Cylinders ... 21 21 
Scraping Carbon from Combustion Cham- 
ber 21 22 

Arrangement of Engine and Auxiliaries . 21 24 

Cold- Weather Hints 21 26 

Gasoline-Handling Precautions 21 28 

Management of Marine Gas Engines 

Location of Engine and Auxiliaries ... 22 1 

Piping 22 10 

Gasoline Tanks 22 IG 

Starting, Running, and Stopping .... 22 21 

Care and Repair of Engine 22 35 

Laying Up the Engine 22 36 

Tools and Repair Parts 22 37 

Management of Stationary Gas Engines 

Selection of Engine 23 1 

Examination of Engine 23 2 


Managexext of Stationary Gas Engines — 

k/^ Secticm Page 

Liian of En^^ine 23 4 

FocscAtion 23 4 

Piping Svsiem 23 10 

Cooling STsiem 23 19 

Assembling Engine and Ac^nstmeni of 

Fins 23 23 

Igniiic^n System 23 29 

Siirrlng ihe Engine 23 32 

Cir« o: Engine Parts 23 41 

Igniter 23 41 

Fcj^^e: VilTCs 23 42 

Ois-C-vrk ..... ... 23 43 

LVv-m.r 23 44 

S:u.r.-7.i r^\-i.>e> .23 45^ lVv-:v>?> . 23 47 

x.-^ .^: MjL::.iier..en: . . 2o 50 

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V *.*. A.,. x*..>- C . . -3^ ^T \>%M 

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« V 

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Troubles and Remedies — Continued Section Page 

Coil Derangements 24 49 

Wiring Troubles 24 50 

Timer Troubles 24 53 

Clogged Muffler 24 54 

Gasoline Leaks .24 55 

Water in Exhaust Pipe or Muffler .... 24 55 

Water in Engine Cylinder 24 56 

Failure to Govern 24 57 

Refitting Piston and Piston Rings .... 24 58 

Repairing Cracked Water-jacket .... 24 60 

Repairing Broken Engine Bed 24 63 

Regrinding Valves 24 64 

Renewing Babbitt-Metal Liners 24 67 

Packing Renewals 24 68 

Power Determinations 

Object of Engine Testing 25 1 

Apparatus Used in Testing 25 2 

Method of Making Engine Tests .... 25 19 

Reports of Tests 25 22 

Horsepower Calculations 25 27 

Heat Losses 25 39 

Indicator Diagrams 25 41 

Shop Tests 25 46 

Efficiency 25 48 


Note. — All items in this index refer first to the section and then to the page of the sccti >\\ 
Thus. "Ammeter, {18, pll" means that ammeter will be found on page 11 uf section 18. 

Adjusting parts, Assembling stationary gas 

engines and, (23, p23. 
Adjustment. Carbureter, §17, p45. 
Coil vibrator out of, {24, p49. 
of ignition devices. 123, p34. 
of lubricators. (23, p32. 
of new automobile- or marine-engine car- 
bureters, 517, p47. 
jiir gap. Length of. {18. p35. 

in explosive mixtures. Proportion of gas 

and. 517, p8. 
inlet. Carbureter with hit-or-miss governed, 

117, p22 
inlet controlled by throttle, Carbureters 

with. 517, p39. 
-mixing chamber. Gas and, (17, plO. 
required for gas engine. Volume of, {25, 
Alden dynamometer, $25, p5. 
Alternating current in charging storage bat- 
teries. Use of, 5I8, pl4. 
Ammeter, 518, pll. 
Amsler planimeter, (25. p29. 
Apparent slip of propeller, 119, p52. 
Area of propeller blades. Developed, $19, p52. 

of propeller blades. Projected, §19, p52. 
Arrangement of automobile engines and 

auxiliaries, $21, p24. 
Assembling governing mechanism. {23. p26. 
stationary gas engines and adjusting parts. 
123, p23. 
Automatic float -feed carbureters. 517, p34. 
inlet valve. Excessive lift of, 524, p23. 
inlet-valve springs. Effect of unequal ten- 
sion of, 524. p23. 
starters for automobiles. 519, p25. 
Automobile battery switch, 518, p>62. 
-engine carbureter, (17, p27. 
•engine carbureters. Regulation of, 517, 

Automobile — (Continued) 

-engine cooling, 519, p34. 

-engine governors, 519, p28. 

engines and auxiliaries. Arrangement of, 
521. p24. 

engines, Care of. 521, pl2. 

engines. Inspection of, 521, pi. 

engines. Location of faults in, 521, pi. 

engines. Retiming the ignition of. 521, pi 9. 

engines. Starting and stopping, 521, pl5. 

engines. Timing valves of, 521, pi 7. 

or marine-engine carbureters. Adjustment 
of new, 517, p47. 

speed change gear, 519. pi. 
Automobiles. Automatic starters for, 519. p25. 

Hand starter for, 519, p24. 

Non-freezing solution for, 521, p26. 
Auxiliaries, Arrangement of automobile en- 
gines and, 521. p24. 

Location of marine engine and, 522, pi. 
Auxiliary spark gap, 518, p35. 

Babbitt-metal liners. Renewing, '524, p67. 

Back firing, 524. p38. 

Bag, Gas. 517, pl2. 

Band clutch, 519, p21. 

Batteries, Care of primary, 518, pll. 

Care of storage, 518, pl4. 

Charging storage, 518, pi 6. 

Electrolyte for storage, 518, pl4. 

Laying up storage, 518, p21. 

Primary, 5 18. plO. 

Renewing storage, 518, p23. 

Secondary or storage, 518, pl3. 

Testing. 521. p9; 524, p45. 

Testing storage. 518, p20. 

Use of alternating current in charging 
storage, 518, pl4. 

Wiring connections for charging st(.»ragt , 
§18. pl7. 



Battery and spark oofl. Installation ci, {23. 

connectors, flS, pl2. 

power. Reserve, 124. p45. 

switch. Automobile, §18, p62 

troubles, (24, p44. 

weak, (24, p44. 
Baumd hydrometer. (18. pl5. 
Bearings, Inspection of. 121, p3. 

Lack of oil in, (24, p25. 
Bevel-gear differential, $19. pi 6. 
Blades, Crowning surface of propeller. (19, p52. 

Cutting edge of propeller, §19, p52. 

Developed area of projieller, (19, p52. 

Driving surface of propeller, (19, p62. 

Projected area of propeller, (19, i>62. 
Blast-fumace gas, Geaning, §20, p33. 

-furnace gas. Composition of, §20, p31. 

-furnace gas for gas engines, §20, p31. 
Bolts, Engine foundation, §23, p5. 
Brake horsepower, §25, p2. 

Prony §25. p2. 

Rope, §25 p4. 
Brakes §19. p22. 

Break m primary wiring circuit, §24, p50. 
Broken engine bed. Repairing. §24. p63. 

exhaust-valve spring. Weak or, §24, p24. 

exhaust-valve stem or key, §24, p24. 

inlet-valve spring, Weak or, §24, p22. 

inlet-valve stem or key, §24, p24. 

piston rings. Sticking and, §24, pl6. 

secondary wiring cable, §24, p51. 

spark-plug porcelain, §24, p45. 

Cable, Broken secondary wiring, §24, p51. 

Grounded secondary wiring, §24, p61. 

Ignition wire, §18, p69. 
Calculations, Horsepower. §25, p27. 
Cams, Slipped valve, §24, p24. 
Carbon from combustion chamber, Scraping, 

Carbureter adjustment, §17, p46. 

Automobile-engine, §17, p27. 

Definition of, §17, pl5. 

Dirt in. §24, p33. 

Disturbances, §24, p30. 

Float too heavy, §24, p35. 

Float too high, §24. p34. 

Float too light or adjusted too few, (24. p35. 

Flooding of, §24. p31. 

Kerosene-engine, §17, p26. 

Testing, §21, p2. 

with hit-or-miss governed air inlet, §17. p23. 

with hit-or-miss governed gasoline inlet. 
§17, p25J. 

with water-spray attachment, §17. p20. 

Carbureters, Adhistment of xww antonBoi3ilB> 
or marine-engine, §17, p47. 

Advantage of spray. §17, pl8. 

Automatic float-feed. §17. p84. 

Central-feed, §17, p42. 

Classification of, §17, pl5. 

Filtering, §17, pl5. 

Float-feed, §17, p32. 

Objections to surface and filterins^ (17. 

Regulation of automobile-engine, |17» p28. 

Spray, §17, pl6. 

Stationary-engine, §17, pl9. 

Surface, §17, pl5. 

with air inlet controlled by throfckle, §17, 
Carburization, §17. pi 4. 
Care and management of stationary su 
engines. §23, p41. 

and repair of marine engines. §22, p35. 

of automobile engines, §21 , pl2. 

of dynamos and magnetos. §18, p59. 

of primary batteries, §18, pll. 

of spark coils. §18, p29. 

of storage batteries, §18. pl4. 
Causes of misfiring, §24, p3. 

of preignition, §24, p40. 

of refusal to start or sudden stoppase of 
engine, §24. p2. 

of slowing-down troubles with marine 
engines. §24, p5. 

of weak explosions, §24. p4. 
Central -feed carbureters, §17, p42. 
Centrifugal gas-cleaning plant, §20, p34. 
Charge, Definition of. §17, p2. 

in cylinders. Order of firing, §18, p39. 

Ovcrrich mixture or, §24. p30. 

Weak mixture or, §24, p32. 
Charging storage batteries, §18. pl6. 

storage batteries. Use of alternating cxtrrent 
in, §18. pl4. 

storage batteries, Wiring connections for, 
§18, pl7. 
Circuit, Break in primary wiring, §24, pSO. 

Short, §24, p48. 
CSrctdating pumps. Types of water, (19, j>39. 
Circulation of cooling water. Obstructed, (24, 

pressure gauge. Water, §19. p42. 

tell-tale. Water, §19. p42. 
Classification of carbureters, §17, pl5. 

of gas producers §20, pi. 
Cleaning blast-fumace gas, §20, p33. 

pipe connections to suction gas producer 
§20, p29. 

plant. Centrifugal gas. §20, p34. 

plant with notary washer. Gas, §20. p33. 



Oearanoe, Finding percentage oC, t25, p84. 
Qogged mufBer, §24, p54. 
Qutch, Band, §19, p21. 

Disk. §19. p22. 

Friction ring, §19, p21. 

transmission system, Individual, §19. p7. 
Clutches. Cone, 119. pl9. 
Cock. Care of gas-, 123, p43. 

Location of sea. 122. pl4. 
Coil condenser. Defective. (24, p49. 

connections. Spark-, flS, p25. 

derangements. 124, p49. 

Installation of battery and sx>ark, |23, p29. 

Short-circuited. 124. p50. 

trembler, Spark-, (18, pp8. 28. 

vibrator out of adjustment. (24, p49. 
Coils. Care of spark. (18, p29. 

Construction and operation of spark, (18, 
Cold-weather hints, (21, p26. 
Combustion chamber. Scraping carbon from. 

knock, (24, pll. 
Commutators or distributors. Secondary, (18, 

Timers or primary. (18. p37. 
Comparison of suction and pressure gas 

producers. (20. p6. 
Compensating gear. Equalizing or, (19. pI5 
Composition of blast-furnace gas. (20, p31. 
Compound pitch. (19. p47. 
Compression and mean effective pressures. 
(25. p38. 

coupling, (19. pl8. 

relief and spark retardation in marine 
engines, (22. p29. 
Condenser, Defective coil, (24, p49. 
Cone clutches. (19. pl9. 
Connecting-rod. Assembling piston and, (23 

Connections. Electrical. (23. p31. 

for charging storage batteries. Wiring, (18. 

Loose electrical, (24. p52. 

Spark-coil. (18. p25. 

Testing electrical. §23. p31. 

to gas producer. Pipe. (20. p23. 

to suction gas producer. Cleaning pipe, (20. 
Connectors. Battery. (18. pl2. 
Construction and operation of spark coils, 
(18. p24. 

of large suction gas producer. (20. pll. 

of small suction gas producer. (20. p8. 
Consumption, Gas. (25. p26. 
Contact point. Dirty. (24, p49. 

Short-time, (24, p48. 

Contacts, Poor electrical, (24, p47. 

roughened by sparking. Timer, (24. p53. 
Converter. Mercury-vapor, (18, pl4. 
Cooling and muffling devices, (19* p33. 

^Automobile-engine, (19, p34. 

by steady water supply, (23, p21. 

Marine-engine. (19. p33. 

radiators. Types of water, (19, p37. 

system for stationary gas engines. Water 
(23. pl9. 

system troubles. Water, (24, p27. 

Tank system of. (23. pl9. 

water. Lack of. (24. p27. 

water. Obstructed circulation of. (24. i>27 

-water tank. (25. pl5. 

water. Temperatixre of. (23. pl9. 
Counter, Revolution, (25. pl7. 
Coupling. Compression, (19. pl8. 

Crab-claw, (19, pl9. 
Couplings. Plain. (19. pl7. 

Universal, (19. pl9. 
Crab-claw coupling. (19. pl9. 
Cracked water-jacket. Repairing, (24, p60 
Crank-case, Level of oil in, (23. p48. 
Crowning surface of propeller blades. (10 

Current leakage. (24. p44. 
Cutting edge of propeller blade, (19. p52. 
Cylinder and piston repair work, (24. p58. 

oil. Lack of, (24. p25. 

packing troubles. (24. pl8. 

Water in engine. (24. p56. 
Cylinders, Improper oil in, (24, p2fi. 

Order of firing charge in, (18. p39. 

Taking off and replacing, (21, p21. 

Scored and leaky, (24. pl2. 


Decreasing pitch. (19, p47. 
Defective coil condenser. (24. p49. 
Delivered horsepower. (25. p2. 
Deposits in water-jacket. (23, p21. 
Derangements, Coil. (24, p49. 
Detonation, (17. pi. 

Developed area of propeller blades, (19, p52 
Diagrams, Explosive-mucturc pressure. (17 

Indicator, (25, p41. 
Differential, Bevel-gear, (19. pi 6. 

gears. Operation of, (19. pl5. 

Spur-gear, (19. pl5. 
Dirt in carbureter, (24, p33. 

or waste in gasoline pipe. (24. p88. 
Dirty contact point, (24, p49. 

radiator, §24. p29. 
Disk clutch, (19, p22. 
Disorders, Spark-plug, (24, p45. 



Displacement. Piston, (25, p22. 
Distributors, Secondary commutatorB or, (18, 

Down-draft gas producer, 120. pl5. 
Driving surface of propeller blades. {19. 

Dynamo as a dynamometer, 125, p7. 

-electric ignition generators, §18. p45. 
Dynamometer, Alden, (25, p5. 

Dynamo as a, $25, p7. 
Dynamos and magnetos, Care of, (18, p50. 

Effect of unequal tension of automatic inlet- 
valve springs, $24. p23^ 
Effective pressure. Mean, $25, p34. 
Efficiency, Engine, (25, p48. 

Mechanical, $25, p49. 

Thermal, $26, p48. 
Electrical connections, $23, p30. 

connections. Loose, $24, p52. 

connections. Testing. $23, p31. 

contacts, Poor, §24, p47. 
Electrolyte for storage batteries. $18, pi 4. 
Engine and auxiliaries, Location uf marine, 
$22, pi. 

bed. Repairing broken, $24, p(i3. 

Causes of refusal to start ur of sudden 
stoppage of, 524, p2. 

cooling, Automobile-. $19, p34. 

cooling, Marine-, 519, p33. 

cylinder. Water in, §24, p56. 

efficiency, $25, p48. 

exhaust. Piping marine-, $22, pl4. 

-foundation bolts. $23, p5. 

Foundation for marine, $22, p3. 

Foundation of stationary gas, §23, p4. 

-ff)un<lation templet, §23, p4. 

foundation. Timber. §23, p8. 

governors, Automobile-, §11), p29. 

governors, Marine-, $19, p32. 

indicator. Gas-, $25, p7. 

ignition mechanism, Marine-, $18, i>4. 

installation, Marine-. i'J'2, pi. 

manaKenu-nt, Routine of stationary ^jas-, 
§23. poO. 

«il>oration, Marine-. §22, X)21. 

starters, Marine-, §19, p20. 

starting and running difficulties, Gas, §24, 

test, Log of Ka<.-, §2"), p20. 
test. Method of making Has-, §25, pl9. 
test. Report of Has-, §25, p22. 
testing. Object of gas . §25, j)]. 
to bed. Fastening marine, §22, p8. 
vibration. Prevention of. §23, p7. 
Volume of air required for gas, §25, p24. 

Engines and adjusting parts. Assembling stir 
tionary gas, (23, p23. 

and auxiliaries. Arrangement of automo> 
bile. (21. p24. 

Blast-furnace gas for gas, (20. p31. 

Care and management of stationary gas. 
(23, p41. 

Care and repair of marine, (22, p35. 

Care of autoniobile. (21. pl2. 

Causes of slowing-down troubles with 
marine, $24, ]>5. 

Compression relief and spark retardation in 
marine, (22. p29. 

Examination of stationary gas, (23 p2. 

Gaseous mixtures for gas, (17, pl. 

Gasoline piping for marine, (22, plO. 

Inspection of automobile. (21, pl. 

Irregular running of. marine, (24, p6. 

Laying up marine. $22, p36. 

Location of faults in automobile, (21, pl. 

Location of stationary gas, (23. p4. 

on floor. Supporting, $23, p8. 

Piping system of stationary gas. $23, plO. 

Retiming the ignition of automobile. |21» 

Reversing gear for marine, $19, pl2. 

Selection of stationary gas, $23, pl. 

Sizes of piping for gas. §23, pll. 

Starting and stopping automobile. (21 , pI5. 

Starting, running, and stopping marine. 
$22, p21. 

Starting stationary gas, $23, pp32, 50. 

Stopping stationary gas, $23, p51. 

Timing valves of automobile, §21, pl7. 

Use of starting bar for marine, $22, p27. 

Use of starting cranks for marine, (22, p26. 

Water-cooling system for stationary gas, 
§23. pl9. 

Water piping for marine, $22, pl2. 
Equalizing or compensating gear, $19, pl5. 
Evaporator, Combined i>roducer and, $20, 

Examination of stationary' gas engines, $23, 

Excessive lift of automatic inlet valve, (24, 

Exhaust pijK.' or muffier, Water in, $24, p55. 

piping. §23, pl3. 

Piping marine-engine, §22, pl4. 

Underwater. §19, p33. 

-valve keys, Replacing. §21, p20. 

-valve spring, Weak or broken, §24, p24. 

-valve stem or key. T3roken, $24, p24. 

valves, Leaky inlet and. §24, p20. 
Expanding pitch, §19. p47. 
P^xplosion of gases. §17, i)l. 
Explosions, Causes ut weak, §24, p4. 



Bxplorive gaseous mixture, {17. pi. 
gaseous mixtures, Measuring changes cf 

pressive in. §17, p3. 
•mixture pressure diagrams, 117, p5. 
mixtures. Proportion of gas and air in, (17, 

mixtures. Rate of fall of pressure in, (17, 

mixtures. Rate of flame propagation in, 117, 



Failure to govern. §24, p57. 

Pa<^ning marine engine to bed, (22, p8. 

Faults in automobile engines. Location of, 

Filling pipes and vents to tanks! Gasoline, (22, 

Filter. Gasoline. 123. pl8. 
Filtering carbureters, §17. pl5. 

carbureters, Objections to surface and, §17. 
Firing charge in cylinders. Order of, §18. p39. 

suction gas producer. §20, p27. 
Flame propagation. §17. p2. 

propagation in explosive mixtures. Rate of, 
§17. plO. 
Float-feed carbureters, §17. p32. 

-feed carbureters, Automatic. §17, p34. 

too heavy. Carbureter. §24. p35. 

too high. Carbureter. §24. p34. 

too light or adjusted too low, Carbureter 
§24. p35. 

^'alve. Leaky carbureter, §24. p34. 
Flooding of carbureter, §24. p31. 
Flywheel. Assembling shaft and. §23, p23. 
Formula. Horsepower, §25, p37. 
Foundation bolts. Engine-. §23, p5. 

for marine engine, §22. p3. 

of stationary gas engine. J23, p4, 

templet. Engine-, §23. p4. 

Timber engine, §23, p8. 
Foundations for gas producers, §20, pl9 
Friction-ring clutch, §19. p21. 
Fuel troubles, §24 p36. 


Gap. Auxiliary spark. §18. p35. 

Length of air. §18, p35. 

Length of spark. §21, p8. 

Safety spark. §18, p27. 
Gas and air in explosive mixtures. Propor- 
tions ot §17. p8. 

and air-mixing chamber. §17, plO. 

bag. §17. pl2. 

Qeaning blast-ftunace. §20. p33. 

•cleaning plant. Centrifugal. §20, p34. 

-cleaning plant with rotary washer. §20, p33. 

Gas— (Continued) 
-cock. Care of, §23, p43. 
Composition of blast-furnace, §20, p31. 
consumption. §25. p26. 
engine. Foundation of stationary. §23. p4. 
-engine indicator, §25, p7. 
•engine management. Routine of stationary. 

§23. p50. 
-engine starting and running difficulties 

§24. pi. 
•engine test, Log of. §25, p20. 
-engine test, Method of making, §25. pl'J. 
•engine test. Report of, §2.'>, p22. 
-engine testing, Object of. §25. pi. 
engine, Volume of air required for, §25, i)24. 
engines and adjusting parts. Assembling; 

stationary. §23, p23. 
enj^ines. Blast-furnace gas for, §20, p31. 
engines. Examination of stationary, §23, p2. 
engines, Gaseous mixtures for. §17, pi. 
engines, Location of stationary, §23. p4. 
engines. Management and care of stationary, 

§23. p41. 
engines, Piping system of stationary, §23, 

Engines, Selection of stationary, §23, pi. 
engines, Sizes of piping for, §23, pll. 
engines, Starting stationary, §23, pi 32, 50. 
engines. Stopping stationary, §23, p51. 
engines. Water-cooling system for station- 
ary, §23, pl9. 
measurement. §25, pl5. 
meter, §23. pl3. 
meters. Sizes of. §23. pl3. 
Piping for natural. §23, pl3. 
pressure. Measurement of. §25, p25. 
pressure. Regulating, §23, p38. 
•pressure regulator, §23, pi 2. 
Process of manufacturing producer. }20, 

producer. Cleaning pipe connections tn 

suction, §20, p29. 
producer. Construction of large suction, 

§20, pll. 
producer, Construction of small suction. §?0. 

producer. Down-draft. §20. pl6. 
producer. Firing suction, §20, i)27. 
producer. Lining the. §20. p20. 
producer. Pipe connections to. §20, p23 
producer, Restarting suction, §20. p2'J. 
producer. Starting suction, §20, ppll, 25. 

producers. Gassification of. §20, pi. 
producers. Comparison of suction and pres 

sure, §20, p6. 
producers. Foundations for, §20, plO. 



Gas — { Continued) 

producers, Mana^ment of, 130, pl9. 

pfoducers. Operation of pressure. {20. p30. 

producers. Operation cf suction. §20 p25. 

producers. Pressure. f20. p4. 

producers. Suction. (20. p6. 

-regulating floor. il7. pll. 
Gaseous niixture. Explosive. §17. pi. 

TTUxtures tor gas engines. §17, pi. 

TT.ixtures. Measuring changes of presstire in 
explosive. §17. p3. 
Oases. Explosion of. §17. pi. 
Gasoline filling pipes and vents to tanks. f22. 

rJter. %23. pl8. 

-handling precautions. §21. p2S. 

inlet. Carbureter with hit-or-n:iss governed. 

leaks. §24. pS5. 

pipe. Dirt or waste in. §24. p33. 

Piping for. §23. pi 7. 

piping frr riarine engines. §22. plO. 

p-.irr.p. Care cf. §23. f44. 

Stale. §24. p36. 

tar.i. §22. pl6. 

Water in. §24. poO. , 

Gauire. Siphcr:. §2o. p2o. 

U. j2o. p2,> 

Water. 52o p25. 

Witercirculaticn pressure. §19. p42. 
Ge^r .\-.:t v^- bile speed -char .re. SlV*. pi. 

viinervr.t'-il B«:vel. §1*.*. pl',« 

dirc:i?r.t-\l. Sp-.:r. Jl;>. p!5 

E ;-.LaI::ir.j: -- . ntpor.satir.;:. §1'.^. pl.'^ 

f r rt'.arir.e t'r.^-ire>. Reverv^rc. §1^?. pi 2. 

J- - ■■J' ■ » •• ■ i^f'- • 

-<'-.a:t. AN^tr::': ".•v.^ v.\lvo. §23. p26 

trar «-:*.•<>• ^n sy>re'r.. Sliding. §1V». p2. 
i'lears. Ch^r.i:: r. .: .".irfervnti.*! §19. plo. 
irt r.€rx'. r* . D vr a • • : • o'.c ct ric i<:r.:t :o r. . § 1 S . ;^4 '• . 
Crverr.. Failv.rv t . §24. pC»7. 
G:^ .:evuY>. S:art:n^ ar..l. §19. p24 

"•t.Var. '..>—.. .X^.^'vV*.:::/. §2-^^. p2tv 
Cr-vcrr.. r. i.\ir\ : $2.%. p4-i. 
Gr-.trr. r*.. A-..: :r V-'.c *r.s'r.. . $10. p2>. 

Ma rr r.e ■ c : v : ■:: J '. \» r :i2 

vr'-ir.. '.«■.: ><:.■ '\ wi^.tv ^a\'lo. J24. :.v»l. 


Hard <tartor • " .»■. *. •'r.b\\'<. $r.». :^2l. 
Hat. he: ;'a:v."-.:i '.'$_.*>. -vl 

Hf^t 1 >.;<'':. $2.'. '.nI;* 

-tcnsis-r. s-w::^:., §1S. ;<H. 

Hints. Cold-weather. 121. p26. 
Uit-or-ndsB governed air inlet. Carbureter 
with. §17. p23. 

-or-nuss go^remed gawnKne inlet. Ckiboreter 
with. §17. p22. 
Horsepower. Brake. §25. p2. 

calculations. §25. p27. 

DeUvered. §25. p2. 

tjrmuia. §25. p37. 

Indicated. §25. p2. 
Hydrometer. Baurae. f 18, pl5. 

Igniter. Care of. §23. pll. 

Examination of \-alvies and. §23. p33. 

plug, §lS. p3. 

troubles. Make and-break. §24. p47. 
Ignition. Dennition of. §17. p2. 

de\-ice*. Ad-ustnaent of. §23, p34. 

generators. Dyaareo-dectric, §18. p45. 

Jun^p-spark. § IS. p7. 

niagnetos, §1S. p47. 

Make-and-break. §18. pi. 

r:Tech.ani5rr.. Sfarine-engine. §18, p4. 

of a-Jtr mobile engines. Retiming §21, plft 

plugs. §23. p30. 

systerr.. Inspection of, §21, p7. 

Titre,:. §17. p2. 

Tin-.-nfe- the. §23. pW. 

wire cable. §1S. p69. 
I:vpr."per oil in cylinders §24. p26. 
Ino.-»rrec: timing. §24. p54. 
Increasing ;:itch. §19. p47. 
Indicated h-"rsep«"wer. §25. p2. 
Indicator diagrams. §25. p41. 

Ga*-eng:r.e, §25. p7. 

Reviucirg :-:.ti. n.-. §25. pl2. 

Speed. §2o. pl7. 
l::.Mv-;iual-. I ■-•.>: 1: * ransmission system. §19, 

lr.^.Arrr-jL*i.r.. FKzration of. §17, p2. 

lr.le: JLr.i cvha.:>t %-a!ves. Leaky. §24. p20. 

valve. E\v-e>-<:ve r.ft of automatic, §24. 

-valve rr.rc. Weak or bmken. §24. p22. 

-valve <rrir.c< ErTect of unequal tension of 
a-::. -at::. §24. p23. 

-va. e <tc"- . r key. Bn-ken. §24. p24. 

N-ulvf": Ir.>iv.-.:. r. . f. §21. p5. 
l">:v.r-. r. . : a-.;:, r-.-bile engines, §21. pi. 

v: Nartr.j:^. §21. p>3. 

\^* icr.-.:: :; >y>:er:'. §21. p7. 

.■:•.:■.'.: '..\lves §21 po. 

. : '•.■.V-^..a:-.r.^ <v>ter'.. §21, p6. 
• \^.v:<.' ,- ■■'".'.•'^ >y<:tfr::s. §21. pll 
l*'>:..*!.ir' V MA">.o-<r..sir.e. §22. pi. 
lrrvf;,."..\r r.-.-r-.: j . :' -Tiarlne engines, §24, p6 



)eposits in water-, (23, p21. 

muffler, (19. p44. 
liversal, (19. pl9. 
ark Ignidon, (18, p7. 

wiring, (18. p68. 


^-engine carbureter, (17, p25. 

)ken exhaust-valve stem or, §24, p24. 

n inlet-valve stem or, (24, p24. 

aldng valve-stem, (21, p21. 

nns exhaust- valve, (21, p20. 

•itches. (18, p60. 

Combustion, (24, pll. 

g due to preignition, (24, pl2. 

nding. (24, p8. 

cooling water, (24, p27. 

nder oil, (24. p25. 

n bearings. (24, p25. 

ction gas producer. Construction of, 


p marine engines, (22, p36. 

rage batteries, (18, p21. 

Current, (24, p44. 
asoline, (24, p55. 
I producer for, (20, p24. 
rburetef float valve, (24, p34. 
;rs. Scored and, (24, pl2. 
id exhaust valves, (24. p20. 
)lug, §24. p47. 

Regrinding. (24, p21. 
[ spark gap. (21. p8. 
lark advance, (18, p38. 
itomatic inlet valve, Excessive, (24, 

lewing Babbitt metal. §24. p67. 

e gas producer, §20, p20. 

ot faults in automobile engines. §21, 

onary gas engines, (23, p4. 
s-engine test, §25, p20. 
rtrical connections. §24, p52. 
eat. §25. p39. 
on magnetos, §18, p49. 
ig devices. Care of, §23, p47 
Inspection of, §21, p6. 
)n troubles, §24. p25. 
rs, Adjustment ot, §23, p32. 
nent of, §23. p29. 


Care of dynamos and §18. p59. 
nsion, §18. p51. 
1. §18. p47. 
ision. (18. p49. 

B(ake-and-break igniter troubles (24, p47. 

-and-break ignition, (18. pi. 

•cmd-break wiring, (18, p65. 
BCaking valve -stem keys, (21, p21. 
Management of gas producers, (20, pl9. 

of stationary gas engines. Care and, (23, 
Marine engine and auxiliaries, Location of. 
(22. pi. 

-engine carbureters, Adjustment of new 
automobile- or, (17, p47. 

-engine cooling, (19, p33. 

•engine exhaust piping. (22, pl4. 

engine, Foimdation for, (22, p3. 

-engine governors, (19, p32. 

-engine ignition mechanism, (18, p4. 

-engine installation, (22, pi. 

•engine operation, (22. p21. 

•engine starters. (19. p26. 

engine to bed. Fastening, (22, p8. 

engines. Care and repair of. (22, p35. 

engines. Causes of slowing-down troubles 
with. (24. p5. 

engines. Compression relief and spark 
retardation in, §22, p29. 

engines. Gasoline piping for. (22. plO. 

engines. Irregular nmning of, (24, p6. 

engines. Laying up. (22, p36. 

engines. Reversing gear for, (19, pl2. 

engines, Starting, running, and stopping. 
(22. p21. 

engines. Use of starting bar for, §22. p27. 

engines. Use of starting cranks for. §22. 

engines. Water piping for, (22. pl2. 
Mean effective pressure, (25,, p34. 

effective pressures, Compression and, (25, 

pitch (19, p55. 
Measurement. Gas (25, pl5. 

of gas pressure, (25. p25. 
Measuring changes, of pressure in explosive 
gaseous mixtures. §17, p3. 

pitch of screw propellen §19, p48. 
Mechanical efficiency, §25. i>49. 
Mercury- vapor converter, §18. pl4. 
Meter. Gas, §23, pl3. 
Meters. Sizes of gas. §23, pl3. 
Method of making gas-engine test §25. pl9. 
Methods of startiiig, §23. p34. 
Miscellaneous troubles. §24, p54. 
Misfiring. Causes of. §24. p3. 
Mixing chamber. Gas- and air-. (17. plO. 

valve. (17, pl3. 

Explosive gaseous, (17, pi. 

pressure diagrams, Explosive. (17, p5. 

in starting. Regulation of, §23, p35. 



H^xxnnt i'jr 9m cofina^ Ga«oas. |17. pi. 
yU%j»irirje[ c^.aa«et *A f>nmr:a^ m ezplosiTe 

tiJittrxiA, §17. p3. 
Vr'.'^jirfj^jci^ 'A JEW afl<! air m explocive, §17. 

SCA^Ur '^ laH of ;/msore in explcmve, §17. 


V.^Ji 'A flarrA {/rvpaipbtion in explosive. 

Ml. pIO. 
*C ;«i*^. O^MSOtA. 124, ;A4. 
> kif*^. |l'^. ji44. 
TT^vrr a exhautt pipe or, 124, i>55. 
W*-.. f :5r. p44. 

U -sf^.if tif'-kef . OxiUng and. (19 p33. 


•iV .r^ grxx. P:;,tr./ f',r. |23. pi 3. 

•• ,r. /r-^nta-^ v/l-jtk/ji for aut/imobfles, {21 . 


''/^/rtri/.t/t'J ciff-ilation <-/£ cooling «-ater. J24. 

^/s: xr. r^Arauei. Laiik of f24. p25. 

:ft '.rhnk^aM:. Levtl of. {23, i*48. 

in '.yitnden. Impr/ijer, §24. p26. 

I^.k of olin'Irr. §24. p2.*i. 

/,r. pi4t//n%. T'^/ much. |24. p27. 
'/;^ratt^/n. Marine -^nifine. |22. p21. 

'/f fJiffervirntial Ke^n. fid pl5. 

'/f pr«*\*ure f(aA pT'Klu/.crs. §20, p30. 

of tfKirk cfAl%, 0>n>truction and. §18, p24. 

of «.<jr ti'^n ga« pT'/^lur.ert. f 2f), p2i>. 
f >rfU r of f.rin;; * harKc in cylinrSers, {18, r>39. 
Ovr-riv h mixture or charKe, §24, p30. 

I'a' king r»;tVM*al*, |24, p6S. 

tr'«;h!#-s. Cylinder, §24, pl8. 
fVr' f-ri'-a^^T of r.l«;aninr:e. Finding, {25 p24. 
Pif.ninK pi -U/n rinKs, §24, pi 7. 
Pif/*- f onmv lion* to Kas pf/duccrs. §20, p23. 

« '#nn#".tions P» s'lction gas pniduter. Clean- 
ing. 120. p20. 

I>irt or wa*.t<: in gascjline, f24, ii33. 
I'tii*'. and vents Vj tanks. Ga valine filling, 122, 

ViiAtiK. ExlauM. 123, pl3. 

for gas engini-s, Sizes of, §23, pll. 

for gaviline. f23, pi 7. 

for marine enKim'^. Cras/jlinc, {22, plO. 

for marine en^im-s, Wat«:r, §22, pi 2. 

for natural ^as, |23, pl3. 

Marini; i-n^^in*- •xl.aMst, §22, pi 4. 

•'iu of -.tati'iiiurv y.u: divines, |23, plO. 
finton and » 'irinn ti«){-rod, AsscinblinK, J23, 


(^KfAMctment^ |25. pfi3. 

Examination of. §23. p33. 

repair work. Cylinder aad. |9^ p68b 

rings, fanning. 124. pl7. 

rings. Refitting pistoii aad, |24. p68. 

rings. Sticking and bcvdoen, §24, plft. 
Pistons, Too tnach oA 00, ^4, pS7. 
Pitch. Compound. }19. x>47. 

Decreasing, f 19. p47. 

Expanding, f 19. p47 

Increasing. 119. p47. 

Mean, f 19. pS5. 

of screw pTopeOer. }10. p46. 

of screw propeller. Measmiiig, |19. |>48L 

of screw propeller. Cnifonn, |10. p47. 

True. §19. p47. 
Plain couplings. §19. pl7. 
Planetary transraiasion system |19, plOl 
Planimeter. Annler. f25. p39. 

Hatchet. f25. p31. 
Plug. Igniter, f 18. p3. 
Plugs. Ignition. f23. p30. 

Requirement of spark, |18, p34. 

Spark, f 18. p31. 
Poppet valves. Oare of. }23. p42. 
Porcelain, Broken qiark-plug. §24. p45. 

Soot on spark-plug. f24. p46. 
Pounding. Knocking or. }24, p8. 
Power. Reserv'e battery. f24, p45. 
Precautions. Gasc^ine-handling, |21t p28. 
Prcigniiion, {24, pi 2. 

Causes of, f24. p40. 

Definition of. §24. p40. 

Knocking due to. }24, pl2. 

Remedies for. f24. p41. 
Pressure diagrams. Explosive mixtuvi, |17 

gas producers, (20, p4. 

gas producers. Comparison of suction and, 
• 520, p6. 

gas pn)duccrs. Operation of. §20, p30 

gauge. Water-circulation, 119, p42. 

in explosive gaseous mixtures. Measuring 
chan>fes of, §17. p3. 

in explosive mixtures. Rate of fall of, §17^ 

Mean efTective, {25, p34. 

Measurement of gas, (25, p25. 

RcgulatinK gas. J23, p38. 

regulator. Gas-, §23, pl2. 
Pressures. Qjmpression and mean effective, 

J25. p'.iS. 
Primary batteries, §18. plO. 

l>atl('rics, Care of, §18, pll. 

cominutaturs, or tiinerb, §18, 1)37. 




wiring circuit. Break in, {24, p50. 

wiring short circuit or ground in, (24, f>51. 
Process of manxifacturing producer gas. (20, 

Producer and evaporator combined, 120, pl3. 

Cleaning pipe connections to suction gas, 
§20. p29. 

Construction of laige suction gas. |20. pll. 

Construction of small suction gas. 120, p8. 

Down-draft gas, (20, pl6. 

Firing suction gas, (20, p27. 

for leaks. Testing. (20. p24. 

gas. Process of manufacturing, (20, p2. 

Lining the g^, (20. p20 

Pipe connections to gas, (20. p23. 

Restarting suction gas, (20, p29. 

Starting suction gas (20, ppll, 25. 

Stopping stiction gas, (20, p28. 
Producers, Classification of gas, (20, pi. 

Comparison of suction and pressure gas 
(20, p6. 

Foundations for gas, (20, pl9. 

Bfanagement of gas, (20, pl9. 

Operation of pressure gas, (20, p30. 

Operation of suction gas, (20, p25. 

Pressure gas, (20» p4. 

Suctkin gas, (20, p6. 
Projected area of propeller blades, (19, p52. 
Prony brake, (25, p2. 
Propeller, Apparent slip of, (19, p62. 

blades. Crowning surface of, (19, p52. 

blsules. Cutting edge of, (19. p52. 

blades. Developed area of, (19, p52. 

blades, Driving surface of, (19, p52. 

blades. Projected area of, (19, p.52. 

Measuring pitch of screw. (19, p48. 

Pitch of screw, (19, p46. 

Slip of, (19. p52. 

Slip of screw, (19, p46. 

Uniform pitch of screw, (19, i>47. 
Propellers, Reversing, (19, p55. 

Types of screw, (19, p45. 
Proportions of gas and air in explosive mix- 
tures, (17, p8. 
Pump, Care of gasoline, (23, p44. 

Gear, (19, p40. 
Pumps, Types of water-circulating, (19, p39. 
p3rroroetcr, (25, pl6. 

Radiator, Dirty, (24, p29. 

Scale or sediment in, (24, p28. 
Radiators, Removal of scale from, (19. p30. 

Types of water-cooling, (19, p37. 
Kate of fall of pressure in explosive mixtures. 
(17. p6. 

Rate — (Continued) 

of flame propagation In exploave mixtures 
(i7, plO. 
Readings, Temperature. (25, p26. 
Reducing motions. Indicator, (25, pl2. 
Refitting piston and piston rings, (24, p58. 
Regrinding leaky valves, (24, p21. 

valves. (24, p64. 
Regulating gas pressure, (23, p38. 
Regidation of automobile-engine carbureters, 
(17, p28. 

of mixture in starting, (23, p35. 
Regtilator, Gas- pressure, (23, pl2. 
Remedies for preignition, (24, p41. 

for slowing-down troubles with marine 
engines, (24, p6. 
Renewals, Packing, (24, p68. 
Renewing Babbitt-metal liners, (24, p67. 

storage batteries, (18, p23. 
Repair of marine engines. Care and, (22, p35. 

parts. Tools and, (22, p37. 

work. Cylinder and piston. (24, p58. 
Repairing broken engine bed, (24, p63 

cracked water-jacket, (24, p60. 
Repairs, (24. p58. 
Report of gas-engine test, (25, p22. 
Reserve battery power (24, p45. 
Restarting suction gas producer. (20. p29. 
Retiming the ignition of automobile engines, 

(21, pl9. 
Reversing gear for marine engines, (19, pl2. 

propellers, (19, p55. 
Revolution counter, (25, pl7. 
Rings, Pinning piston, (24, pl7. 

Refitting piston and piston, (24, p58. 

Sticking and broken piston, (24, plG. 
Rope brake. (25, p4. 
Rotary washer. Gas-cleaning plant with. (20. 

Routine of stationary gas-engine manaffp- 

ment, (23, p50. 
Running, and stopping marine engines. 
Storting, (22, p21. 

difficulties. Gas-engine storting and, (24. pi . 

Safety spark gap, (18, p27. 

Scale from radiators, Removal of, (19, p39. 

or sediment in radiator, (24, p28. 
Scored and leaky engine cylinders, §24, 

Screw propeller. Measuring pitch of, (19, p48. 

propeller. Pitch of. (19, p46. 

propeller. Slip of. (19, p46. 

propeller, Unifonn pitch of. (19, p47. 

propellers. Types of, (19, p45. 
Sea cock. Location of. (22, pl4. 



Secrmdary oommtitaton or Sstxibntors, f 18. 

or itongt batteries. flS. pl3. 

wiring cable. Broken. f24. p51. 

wiring caUe. Grounded. f24. p51. 
Sediment in radiator. Scale or. f24. p28. 
Selfcctir/n of stationary gas engines. f23. pi. 
Shaft and flywheel. Assembling f23. p23. 

Assembling valve gear, f23, p26. 
Shop tests. f25. p46. 
Sb/^irt circuit. §24, p48. 

circuit or grotmd in primary wiring, (24, 

•circuited coil 124. p50. 

'time cr>ntact. f24, p48. 
Siphr/n gauge. f25. p25. 
Sizes of gas meters, {23, pl3. 

of piping for gas engines, {23. pll. 
Stiding'gear transmission system, {19, p2. 
Slip of prrjpeller. f 19. p52. 

of propeller. Apparent, §19, p52. 

of screw propeller, §19, p46. 
Slipped valve cams, 124. p24. 
Siowing-down troubles with marine engines. 

Causes of. (24, p5. 
Small suction gas producer. Construction of, 

120. p8. 
Snap switches. {18, pM. 
i>if,X on spark-plug porcelain, {24. p46. 
Sfjark advance lever, §18. p38. 

-c'/il connecti^^ms, §18, p25. 

c'Al, Installation of battery and. f23, p29. 

-c*jil trembler. §18. pp8. 28. 

cr/Us. Care of. §18. p29. 

cMs, Construction and operation of, §18, 

gap, Auxiliary, §18, p35. 

gap. Length of. §21, p8. 

gap. Safety. §18. p27. 

-plug di.srjrders, §24, p45. 

plug. Leaky, §24, p47. 

-plug pr^rce'ain. Broken, §24, p45. 

-plug pr>rcelain. Soot on, §24, p46. 

plugs. §18, p31. 

•{/lug's requirements, §18, p34. 

retardation in marine engines, Compressior 
relief and. §22. p29. 

timing. Testing. §21, plO. 
Sjiarking, Timer contacts roughened by, §24, 

Sfieed-change gear. Automobile, §19, pi. 

indicator, §25, pi 7. 
Spray carbureters, §17, pl6. 

(arburetera. Advantage of, §17, pl8. 
Sprinn, W<*ak or bnjken cxhaiist-valve, §24. 
p24 . 
WVak or broken inlet- valve, §24, p22. 

Springs, Effe ct oi iinr qiuu tgnsioo at tnto 

matic inlet-valve. §24, p23. 
Spur-gear differential. §19, pL5. 
Scrubber. Pilling the. §20. p22. 
Stale gasoline. §24. ii36. 
Start or of sudden stoppage of engine. Causes 

of refusal to. §24. p2. 
Starter for automobiles. Hand. §19, p24. 
Starters for automobiles. Automatic. §19. p25. 

Marine-engine. §19. p26. 
Starting and governing de^-ices, §19, p24. 
and running difficulties. Gas-engine. §24. pi. 
and stopping automobile engines. §21. pl5. 
bar for marine engines. Use of, §22. p27. 
crank for marine mginrs. Use of, §22, p28. 
devices. Care of. §23. p45. 
Difficulties in. §23. p35. 
Methods of. §23. p34. 
Regulation of mixture in. §23. p35. 
ninning. and stopping marine engines, §22. 

stationary gas engines. §23. pp32. 50. 
suction gas prodticer, §20. ppll. 25. 
Stationary-engine carbureters, §17, pl9. 
gas engine. Foundation of. §23. p4. 
gas-engine management, Routine of. §£3, 

gas engines and adjusting parts. Assem- 

bUng. §23. p23. 
gas engines. Examination of, §23. p2. 
gas engines. Location of, §23, p4. 
gas engines. Management and care of. §23, 

gas engines. Piping system of. §^. plO. 
gas engines. Selection of. §23. pi. 
gas engines. Starting. §23. pp32. 50. 
gas engines. Stopping. §23, p51. 
gas engines. Water-cooling system for, §23. 
Sticking and broken piston rings, §24, pi 6. 
Stoppage of engine. Causes of refusal to start 

or of sudden. §24, p2. 
Stopping automobile engines. Starting and. 
§21, pl5. 
marine engines. Starting, running, and, 

§22, p21. 
stationary gas engines, §23, p51. 
suction gas producer. §20. p28. 
Storage batteries, Care of. §18. pi 4. 
batteries. Charging, §18. pl6. 
batteries. Electrolyte for, §18. pi 4. 
batteries, Laying up, §18, p21. 
batteries. Renewing, §18, p23. 
batteries, Secondar>' or. §18, pl3. 
lotteries. Testing. §18, p20. 
batteries. Use <tf alti'rnaling current in 
char^nng. §>8. pll. 



Storai^c — (Continued) 

batteries. Wiring ooimectiona for chaxging, 
{18, pl7. 
Suction and pressure gas producers. Compari- 
son of, {20, p6. 

gas producer. Qeaning pipe connections to, 
{20. p29. 

gas prodxioet. Construction of large, {20, 

gas producer. Construction of small, {20, p8. 

gas producer. Firing, {20. p27. 

gas producer. Restarting, {20, p29. 

gas producer. Starting. {20, ppll, 25. 

gas producer, Stopping. {20. p28. 

gas producers, {20. p6. 

gas producers, Operation of. {20, p26. 
Supporting engines on floor. {23. p8. 
Sitrface and Altering carbureters. Objections 
to. {17. pl7. 

carbtueters, {17, pl5. 

of propeller blades. Crowning, {19, p52. 

of propeller blades. Driving, {19, p52. 
Switch, Automobile battery, {18, p62. 

High-tension, {18, p64. 
Switches. Knife. {18, p60. 

Snap. {18. p64. 
Synchronism, {18, p48. 

Tachometer, {25. pl8. 
Tank. Cooling-water. {25. pl6 

Gasoline. {22. pl6. 

system of cooling, {23. pl9. 
Tanks, Gasoline filling pipes and vents to 

{22, pl8. 
Tell-tale water circulation. {19. p42. 
Temperature of cooling water. {23. pl9. 

readings, {25. p26. 
Templet, Engine-fotmdation, {23, p4. 
Tension of automatic inlet-valve springs. 

Effect of unequal, {24, p23. 
Test, Log of gas-engine, {25, p20. 

Method of making gas-engine. {25, pl9. 

Report of gas-engine, {25, p22. 
Testing carbureter, {21, p2. 

batteries. {21, p9, {24, p45. 

electrical connections, {23, p31. 

Object of gas-engine. {25, pi. 

producer for leaks, {20, p24. 

spark timing, {21. plO. 

storage batteries, {18. p20. 
Tests. Shop. {25, p46. 
Thermal efficiency, {25. p48. 
Throttle, Carbiuneters with air inlet controlled 

by. {17. p39. 
Timber. Engine-foundation, {23. p8. 
Time of ignition, {17. p2. 

Tinnier contacts roughened by sparking, {24, 

troubles, {24, p53. 

wabbling. {24, p53. 
Timers or primary commutators, {18. p37. 
Timing, Incorrect, {24, p54. 

Testing spark, {21, plO. 

the ignition, {23, p40. 

valves of automobile engines. {21, pl7. 
Tools and repair parts, {22, p37. 
Transmission system. Individual-clutch. {19, 

system. Planetary, {19, plO. 

system, Sliding-gear, {19. p2. 
Trembler, Spark-coil, {18, pp8, 28 
Troubles, Battery. {24. p44. 

Cylinder-packing, {24, pl8. 

Fuel, {24, p36. 

'Lubrication, {24, p25. 

Make-and-break igniter, {24, p47. 

Miscellaneous, {24, p54. 

Timer, {24, p53. 

Water-cooling system, {24, p27. 

Wiring, {24, p50. 

with marine engines. Causes of dowin^ 
down, {24, p5. 
True pitch. {19, p47. 


U gauge, {25, p25. 
Underwater exhaust. {19. p33. 
Uniform pitch of screw propeller, {19, i>47. 
Universal couplings, {19. pl9. 
joint. {19. pl9. 

Valve cams. Slipped, {24, p24. 

Excessive lift of automatic inlet, {24, p23. 

gear shaft. Assembling, {23, p26. 

keys. Replacing exhaust, §21. p20. 

Leaky carbureter float. {24, p34. 

Mixing. {17. pl3. 

spring, Weak or broken exhaust-. {24. |)21, 

spring. Weak or broken inlet-. §24, p22. 

springs. Effect of une(]ual tension of autj- 
matic inlet , {24, p23. 

stem or key. Broken exhaust , {24, p24. 

stem or key. Broken inlet , §24, p24. 
Valves and igniter. Examination of. {23. p33 

Care of poppet, §23. p42. 

Inspection of inlet. §21, p5. 

Leaky inlet and exhaust, {24, p20. 

of automobile engines. Timing, {21, pl7. 

Regrinding, §24, p64. 

Regrinding leaky, §24, p21. 
Vaporizers, §17, ppl6, 29. 

Disadvantages of, {17. p32. 



Vents to tanks, tiasoline filling pipes and, (22, 

Vibration, Prevention of engine, §23, p7. 
Vibrator out of adjustment. Coil, $24, p49. 


Wabbling timer. §24. p53. 

Waste in gasoline pipe. Dirt or. $24. p33. 

Water-circulating pumps. Types of, $19, p39. 

-circulation pressure gauge, $19, p42. 

-circulation tell-tale, §19, p42. 

-cooling radiators, Types of, §19, p37. 

-cooling system for stationary gas engines, 
§23, pl9. 

-cooling system. Inspection of, §21, pll. 

-cooling system troubles, §24, p27. 

in engine cylinder, §24, p66. 

in exhaust pipe or muffler, §24, p65. 

in gasoline, §24, p36. 

gauge, §2o, p25. 

-jacket. Deposits in, §23, p21. 

-jacket. Repairing cracked. §24, p60. 

I^ck of cooling, §24, p27. 

Obstructed circulation of cooling. §24, p27. 

Water — (Continued) 

piping for marine engines. §22. pi 2. 

-spray attachment. Carbureter with, §17. 

supply. Cooling by steady. §23, p21. 

tanks. Cooling, §25, pl7. 

Temperature of cooUng. §23, pl9. 
Weak battery, §24, p44. 

explosions. Causes of, §24. p4. 

mixture or charge, §24, p32. 

or broken exhaust- valve spring;. §24. p24. 

or broken inlet-valve spring, §24. p22. 
Wet muffler, §19, p44. 
Wire cable. Ignition, §18, p69. 
Wiring cable. Broken secondary. §24. p51. 

cable. Grounded secondary, §24. p51. 
Wiring circuit, Break in primary, §24. p50. 

connections for charging storage batteries. 
§18. pl7. 

Jump-spark. §18, p68. 

Makc-and-break, §18. p65. 

Short-circuit or ground in primary, §24, 

troubles. §24. p50. 





1. An explosion is an extremely rapid combustion 
accompanied by the formation of gases and increased pres- 
sure. A mixture of two or more suj^stances whose chemical 
combination will cause an explosion is called an explosive or 
an explosive mixture. There are also many chemical 
compounds that will decompose into gases and vapors, the 
decomposition producing an explosion. These are also 
termed explosives. When the substance exploding is con- 
fined in an unyielding receptacle, there is little or no noise; 
but when the rise of pressure is transmitted to the surround- 
ing air, as when the explosive is wholly or partially uncon- 
finedy the explosion is accompanied by a rapid expansion and 
usually by a. loud noise, or report. If the entire mass of the 
mixture explodes instantly, it is said to detonate, and the 
explosion is called a detonation. All detonating compounds 
can be exploded by percussion, that is, by a blow or jar. 
The best known example of the ordinary explosive is gun- 
powder. Nitroglycerin and the substances derived from it, 
dynamite and giant powder, are examples of detonating 

Cffyrif^kitdhy International Textbook Company. Entered at Stationers' Hall^ London, 




When a combustible gas or vapor and air are mixed in 
proper proportions and ignited, the combination of the gas 
with the oxygen of the air is so rapid as to produce an explo- 
sion. The sudden rise of pressure produced is made avail- 
able for driving a gas engine. 

2. Gases available for engine purposes vary so much in 
their behavior when ignited in the gas-engine cylinder that a 
knowledge of their performance is of great value to the 
operator. Certain effects are produced when an explo- 
sive mixture is confined in a closed vessel without the oppor- 
tunity of expansion such as it has in the gas engine. These 
effects relate to inflammation of the gas, duration of maxi- 
mum pressure, and rate of fall of pressure. The relation of 
these to the proportion of gas and air in the cylinder of a 
gas engine is ver)^ important. 

3. Igrnitlon. — The operation of setting fire to the gase- 
ous mixture in the engine cylinder by means of a device called 
an Igniter is called i^uriiitioii. The moment ignition begins 
is called the time of igrnitiou. The quantity of the mixture 
of gas and air taken into the cylinder at one time is called 
the cliarpro, and when all of it is ig-nited, it is said to be 
wliolly iullanied. The time elapsing between the time of 
ignition and the moment when the gas is wholly inflamed is* 
known as the diinitiou of inHniuniation or duration of 
the explosion. The velocity with which the flame is gen- 
erated in the charge is called the i-ate of flame propagra- 

•1:. Pivssiire CUauflres. — WTien the burning mixture has 
reached its maximum pressure, a short time may elapse before 
the pressure bc\:rins to full to that of the atmosphere. This 
time is the duration of lunxlniuui pressure. The time 
elapsing between the moment when the pressure commences 
its fall from the maximum pressure and the moment when the 
pressure reaches that of the atmosphere is the duration of 
fhll of pressure. The velocity with wb.icii this fall of pres- 
sure takes place is the i-aito of fall of pi*essure. 



5. Apparatus for Moasurlug Pressure Cliaiiires. — An 

apparatus for measuring the changes of pressure in explosive 
mixtures when ignited is shown in Fig. 1. It consists of the 
explosion chamber a, similar to a gas-engine cylinder. The 
interior of thechamberis connected by means of the passage ^ 
to the cylinder c of an indicator. The pressure in a, acting 
on the piston rf of the indicator, compresses the spring e and 

moves a pencil/ bearing against the dram g. The dram is 
rotated by means of the clockwork shown. Motion is given 
to the clockwork by the weight A, and the speed of the 
dram ia controlled by the fan governor ('. The clockwork 
rotates the drum at a constant speed, so that vertical lines 
drawn on the surface of the drum at equal distances apart 
win divide it horizontally into equal spaces indicating equal 
intervalfl of time. 



I— I 


\ iv 

V ' 

\ — s 

r ^-^ — X — ^ 
V' X ^ I. 


» 1 t 5 S' S 



6. The method of using this apparatus is to fill the 
chamber a with a mixture of gas and air in known propor- 
tions, and to ignite the mixture by means of an electric spark. 
The drum having previously been provided with a removable 
card and set in motion, the pressure generated by the explo- 
sion compresses the indicator spring, raising the pencil, 
which draws a line on the card. If the caj-d were now 
removed and laid out flat, the diagram would be similar to 
one of those shown in Fig. 2, which is a collection of dia- 
grams, made with different proportions of illuminating 
gas and air, all the gas used being of the same kind. The 
vertical distances represent pressures in pounds per square 
inch above atmosphere, and the horizontal distances repre- 
sent parts of a second. The explosion chamber used in 
these experiments was 7 inches in diameter by 8^ inches 
high, or a trifle less than -^ of a cubic foot in volume. 

7. Pressure Dlagrrams. — There are nine diagrams in 
Fig. 2, each one showing the various pressures, during dif- 
ferent parts of 1 second, for the explosion and other per- 
formances of the different mixtures. Each diagram is indi- 
cated throughout l)y a line of different construction than the 
others, and is marked by a letter of the alphabet. The mix- 
tures corresponding to each diagram are as follows: 





1 1 









Volumes of Air to i Volume of Ga s 


All diagrams begin at the lower left-hand comer, this 
being the point indicating the time of ignition. From this 
point, the pressure rises more or less rapidly to the point of 
maximum pressure, remains there for a short time, and then 
falls slowly as the cylinder walls absorb the heat generated 
by combustion. 

8. The mixture a reaches its maximum pressure of 40 
pounds per square inch in .39 second after the time of ignition, 
when the pressure remains at a maximum for .08 second, and 


then falls gradually to atmospheric pressure. At the expira- 
tion of 1 second, the pressure within the explosion chamber is 
19.5 pounds per square inch. 

The mixture c reaches its maximum pressure of 60 pounds 
per square inch in .'24 second, the pressure remains at a maxi- 
mum for .025 second, and at the end of 1 second it has fallen . 
to 19 pounds per square inch. 

The mixtures/", g^ and // give nearly the same maximum 
pressures, namely, 87 pounds, 90 pounds, and 91 pounds, 
respectively. The duration of the explosion is .065 second 
for/, .045 second for gy and .055 second for A, The wavy 
condition of the summits of the lines is due to the vibration 
of the indicator spring. All three of these diagrams slope 
do^vnwards immediately after the maximum pressure is 
reached. The fall of pressure is very slow at first, and the 
rapid drop does not begin for several hundredths of a second. 
For practical purposes, the maximum pressures may be said 
to last about .04 second for g and //, and .02 second fory. 
Diagrams^ and // after they cross the .2-second line continue 
practically as one line until they cross the 1-second line at a 
point indicating a pressure of 15 pounds per square inch. 
Diagram/ crosses this line at the 16-pound mark, or just 1 
pound above the point crossed by g and //. Diagram i shows 
the peculiar behavior of a mixture containing one part of 
gas to four parts of air. There is a gradual rise of pres- 
sure for .08 second to 60 pounds per square inch, and from 
this point the pressure increases by a series of jumps until it 
reaches 80 pounds per square inch, .16 second after the time 
of ignition. This ** jumping" is an effect invariably pro- 
duced when the amount of air in the mixture is considerably 
less than that required for the complete combustion of the gas. 

It should be noted that in all these experiments the gases 
arc at atmospheric pressure before ignition. If they were 
compressed to a higher pressure before ignition, the rate of 
flame propagation would be much more rapid. 

9. Rate of Fall of Pressure. — The rate of fall of pres- 
sure is shown by the diagrams to be very nearly the same for 


all mixtures. This can be realized most readily by noting 
that all the diagrams are nearly parallel after the lapse of .5 
second. The rate of fall varies from point to point, the pres- 
sure falling more slowly toward the latter part of the dia- 
gram. If the rate of f ^11 were uniform, this portion of the 
diagram would appear as a straight line. Suppose, for exam- 
ple, that the fall of pressure of diagram h was uniform after 
a lapse of .4 second. Diagram h crosses the .4 line at a 
pressure of 35 pounds, and the 1-second line at a pressure of 
15 pounds; the fall of pressure for .6 second would then be 
35 — 15 = 20 pounds, or 20-4- 60 = -J^ pound for each .01 
second. Then, at the .5 line the pressure should be 35 — ^ 
(50 - 40) = 35 - 3| = 31| pounds. 

In the same manner, it is found that the pressure at the 
.6-second, .7-second, .8-second, and . 9-second lines should be 
28J pounds, 25 pounds, 21f pounds, and 18^ pounds, respect- 
ively. If a straight line is drawn through the points where 
the .4-second line and the 35- pound line cross, and the 1-sec- 
ond line and the 15-pound line cross, it will be found that 
the line passes through the five points just mentioned, but 
that the line of the diagram lies below the straight line. A 
number of short straight lines can be drawn that will coincide 
with the diagram. One of these short straight lines will 
show the rate at which the pressure is falling at that i)art of 
the curve, by continuing it until the amount of its slope can 
be easily determined. A better way is to draw a straight 
line just touching the curve at the point where the rate of fall 
is to be determined. A line that just touches a curve and 
does not pass through it is a tangent. 

If it is desired to find the rate of fall at the point .45, 
draw a tangent xy to curve at this point, and find that it 
crosses the 0-second line at a point indicating a pressure of 
57 pounds per square inch, and the 1-second line at the point 
of pressure; hence the rate of fall at point .45 is 57 — 
= 57 pounds per second. After diagram e passes the . 8 line 
it will be seen to be practically a straight line ; and if it is con- 
tinued backwards as a straight line, it will cross the 0-second 
line at a point indicating about 32 pounds pressure. The 



rate of fall is then 32 — 16 = 17 pounds per second. If this 
rate is the same until the pressure falls to pounds, the 
pressure will be equal to zero in 15-^17 = .883 second after 
passing the 1-second line, or in 1 + .882 = 1.882 seconds 
after the time of ignition. 

In the same manner, the rates of fall and the time of 
reaching zero pressure for any diagram of this nature may 
be found. 

10. Proportion of Gas and Air. — The best proportion 
of gas and air to use for any gas, in an engine having no com- 
pression, is not usually that which has the greatest explosive 


PBOi-oirrioNs of mixtures and rksultino 




















































































power. The best proportion is tliat which gives the highest 
pressure for the quantity of gas used. For the purpose of 
illustration, consider the distance between the en^ of the cyl- 


inder and the end of the piston to be exactly 1 inch; then, for 
each cubic inch contained in this space, there will be 1 square 
'inch on the surface of the piston. The mixture that will 
give the highest pressure for the same quantity of gas can 
be calculated as follows: For instance, take the mixture con- 
taining one volume of gas to five volumes of air. In 'Table 
I, in which the results of the foregoing experiments are tabu- 
lated, the maximum pressure for this mixture is given as 91 
pounds per square inch. Since there are five volumes of air 
and one volume of gas, for each cubic inch of gas there will be 
six volumes of the mixture and to each cubic inch of gas, in 
a layer 1 inch deep, there will be 6 square inches of the mix- 
ture. Hence the pressure of 91 pounds per square inch is 
exerted on 6 square inches, and the total pressure exerted by 
each cubic inch of gas is 91 x 6 = 646 pounds. 

The mixtures giving the highest pressure for 1 cubic inch 
of gas are seen to be those having one volume of gas to twelve 
of air, and one volume of gas to nine of air. 

11. The mixture giving the best mean pressure for the 
first .2 second is that giving 663 pounds to each cubic inch of 
gas, or the mixture containing one volume of gas to twelve 
volumes of air. If the power stroke could be considered as 
taking place without increasing the volume of the space 
occupied by the gaseous mixture, the pressure remaining at 
the end of .2 second after the maximum pressufe has been 
reached would be that given in column 7, and the mean or 
average pressure at the end of .2 second after explosion 
would be that given in column 8. Column 8 gives a means 
of comparison of the power to be obtained in using the 
mixtures indicated in column 1. Thus, the mixture having 
one volume of gas to thirteen of air is more than twice as 
powerful as that having one volume of gas to four volumes of 
air, or in the ratio of 640 to 315, considering the power available 
during the first .2 second after explosion. Of course, there 
is no such thing as an engine running without increasing 
the volume of the cylinder contents, but this assumption is 
made in order to give a method of comparing the various 


mixtures. The gas in each case must also be considered as 
being so exploded as to have the time of maximum pressure 
always at the beginning of the stroke. 

1J3. Ilato of Flame Propagration. — The velocity or 
]*iite of flaiuo propas:atlo]i is shown approximately in 
I^'ig. 2 by the time elapsing between the time of ignition 
and the maximum pressure. The rate of flame propagation 
is approximately the velocity with which the pressure rises 
after ignition. There have, however, been a number of 
iiuicixjiidcnt experiments made with apparatus designed 
expressly for the purpose. In this apparatus, the mixture 
was confined in a tube from which the gas escaped at a 
velocity that could easily be measured. The escaping gas 
was then ignited, and the pressure gradually reduced nntil 
I ho llame rushed back into the tube. The velocity of the 
escaping gas was then just equal to the velocity of flame 
pro^Kigalion in the mixture. This property of explosive 
mixtuivs bocomcs less and less important as the pressure in 
I ho >;as engine, Ix^fore ignition, increases, because the 
higher the pivssure at the time of ignition the more rapid is 
the rate oi tlame propagation. 


tH. Mixing C'hainlH^r. — The usual way of creating a 
v.\MulnistiMo mixture of gas and air for use in a gas engine 
is lo mtiXKhivx* the >ias inio a mixing chamber through which 
I ho air is drawn inimodiatolv l>cfore it enters the cvlinder. 
T*u* \:as ontoi^ the mixing chamber through a small poppet 
valvo that is o^xMiod moohaTiically by a cam or similar 
v-oxivO. .it I ho prv^^xM- tinu\ the an\i of the opening of the 
>:,is \,v*\o N^i*.\v:' *.n piVjVMnivMi to the oiiantiiy of gas to be 
sv.'.^:^'.'.ovl. r**.o nv.vinv; ohan^. Ix^r :s usually a part of the ga*- 
ovc''^\ -ii'-vl *.^ .;:mo'h\; to t>.o oy!*v.v'.or as shown in Fig. 3. 
y'*o ;; ;s 'v.^sNO^ :*v.\^v.v:-'i t>.o v.i'vo .: i:::o the mixing cham — 
! v \ NX ' V * o .. r o • ^ : o :^ ,; : . . A t . :* i s shown the inlet valves 
tx- :V.x* ox *v.v.x^v , ; ,;v.v: .;: < tV.o oxh,i::st \-aIve, The inle1C=- 
x,\'\x ■ '.N ,; -N^^^'v*. \.;'\x\ V :wv\: Vv the oressure in th< 




mixing chamber when the pressure in the cylinder is reduced 
by movement of the piston g on the suction stroke. The 
exhaust valve /is opened mechanically through a cam and rod 
rotating on the lever h. The gas valve a is also opened 

Fig. 8 

mechanically and closed by a spring, thus admitting a more 
definite quantity of gas to the mixing chamber than a pop- 
pet valve controlled only by a spring. 

14. Begrulatln^ Flo^v of Gas. — It is necessary to 
operate the gas valve a mechanically, for the reason 
that the gas is under a certain degree of pressure, and if 
the valve were opened by suction the exact amount of gas 
going through would be somewhat uncertain. On the other 
hand, the fact that the gas pressure is likely to fluctuate 
renders it necessary to control the flow of gas to the gas 
valve by a regulating valve that may be adjusted by hand. 
This regulating valve is shown at a^ Fig. 4. It is provided 
with an index and notches showing exactly how far it is 
opened. When an engine is run on illuminating gas, it is 
generally necessary to reduce the opening of the regulating 
valve slightly at certain hours and increase it a little at 
others, owing to fluctuation in the pressure of the gas in the 



street mains. The gas as it conies from the main and sup- 
ply pipe passes first through the meter 6, then through the 
shut-off valve c, gas bag </, and the regulating valve a. 

The gas bag, which is simply a strong rubber bag with 
connecting tubes at both ends, is employed with all gas 
engines using gas under pressure, to equalize the flow of 

Fic. * 

the gas. Between suction strokes this bag expands owin s 
to the pressure of she jras. and when the suction strt>lK.< 
iw-.'.rs the gas is taken o/,iiokly into the engine, partia-ll" 
co'.lat^ing '.ho t\»ir, .inil conseniiently reducing the press**-"^* 
\v;;h:n ii :o alx>iit o: il-.e atmosphere. By the use ^■ 
this ce\-ice. the gys pressure at the inlet valve is k^^'M 


approximately constant between the beginning ana end of 
the suction stroke, without the use of specially large piping 
to carry the gas, as would otherwise be required. 

15. The fact that the gas is underpressure, while the 
air to be mixed with the gas is not, also has an influence on 
the operation of the gas engine. If the engine runs very 
slowly, the gas will enter the mixing chamber continuously 
under its own pressure while the gas valve is open, regard- 
less of the speed of the engine, while the air is drawn 
through only in response to the suction of the piston. Con- 
sequently, a larger proportion of gas will be taken in at 
slow than at high speeds of the engine. In order to pre- 
vent this and maintain an equal mixture at all speeds, the 
gas-regulating valve must be adjusted by hand to suit 
changes of speed. As engines of this sort are mostly used 
in stationary work and run at a constant speed, this feature 
is not very important, except when the engine is started, 
at which time it may be troublesome, since a mixture of gas 
and air in which the proportion of gas is too great will not 
ignite. The operator must learn by experience the exact 
position at which the gas-regulating valve should be set, 
when the engine is turned over slowly, to produce the right 
mixture for the first explosion. Most of the trouble of 
inexperienced men in starting gas engines arises from their 
lack of care and judgment in managing the regulating valve. 

16« Mixing: Valve. — Another mixing device used in 
connection with a mechanically opened inlet valve for regu- 
lating the proportions of gas and air consists of a suction 
valve arranged to close simultaneously an air inlet and a 
gas inlet. It opens of course more or less according to the 
intensity of the suction, and it is made as light as possible 
so as not to require any greater amount of suction than is 
necessary to open it. This kind of mixing valve, as it is 
called, is used only when the engine is regulated by means of 
a governor, which controls a throttle valve located between 
the mixing valve and the mechanically opened inlet valve. 




An iirrans^cment of this sort is shown in Pig. 5, in which a 
iH the cumbuHtion chamber; b, the exhaust valve; c, the 
.nuchiiiiiciilly opened inlet valve; li, the throttle valve; e, 
the air intake; /, the gas intake; g, the suction-lifted mix- 
inji viilve that opens both the air and the gas passages at 
Uio Biinic time; and h, the water-jacket. In this device. 

^o jTovomor riitates tho throttle valve d as the speed rises; 
i:i w he;i the S]X'<.\1 l»ei.\>mes excessive the passage is closed 
"ov.j;':: :o r(.\:»;vX" the charge taken into the cylinder to the 
iV-.-ire.; .in'.i>-,:nt. 

jx-:i-.;cs :hcsL> simple derices for producing a UQiform 
::x:-,:tv .:' a::^; air, tlwTV is a large number of special 
:;v;-;s :.7 ,<\v.o;.i] nie^s ar.i,i s'.xviol tvpes of engines, the 
■•.■#; i~-.-.vr;.ir.: o: wV.ioh w." Iv ivnsidered later. 


■ :-.■.;•'". -.T .V cv.s t:~jr-"-e is a gaseous mixtnre 
. i-v.rVr., .\-.^ Air, 1: is prwdaced by mixing 
-:" >,v»=r.v,ir'S.-ia wiih air, Tlie hydrocarbon ia 


a substance containing hydrogen 4ind carbon in such a form 
as to bum readily with the proper mixture of air. Gas 
engines located so that they can be supplied with natural or 
artificfal gas will usually receive such fuel; but when not so 
situated, they will be supplied with fuel in the form of car- 
burized air. The most convenient form of hydrocarbon for 
this purpose is the liquid form, such as gasoline, alcohol, 
and kerosene. These liquids can be readily transported in 
tanks and they are obtained directly as a product of nature, 
needing only to be distilled, refined, or purified. 

The evaporation or vaporization of these liquids and the 
mixing of the vapor with air is called carburizatlon. 



IS. Classlflcatlon of Carbureters. — A carbureter is 

an appliance for vaporizing liquid hydrocarbons by pass- 
ing air either over the surface of or through the mass of the 
liquid or by atomizing the liquid and mixing it with air. 
The air thus becomes saturated with the vapors of the 
hydrocarbon. This mixture invariably contains too large a 
proportion of vapor for an explosive mixture; therefore, 
before the mixture can be exploded in the engine cylinder it 
requires the further addition of air. 

Carbureters may be divided into three classes, as follows : 

1. Those which use a large surface of the hydrocarbon, 
generally spread out in thin layers, and over which air is 
compelled to pass. These, for the sake of convenience, will 
be called surface carbureters. 

2. Those in which the liquid fuel is placed in any con- 
venient reservoir, usually of great depth, in proportion to 
the horizontal dimensions, and the air is compelled to pass 
through the body of the liquid. These may be called fll- 
terixt^ carbureters. 

3. Those which vaporize or atomize the hydrocarbon and 





Inject it into a current of air. These may be calledspivr 
carbureters, or vaporizers. 

The first two tj-pes preceded the third in point of time, 
but the spray carbureters are now used almost entirely. 

10, Spray Carbureters. — A good example of a spray 
carbureter or vaporizer is shown in Fig. 6. It is used in 
tftinnectiou with stationary gasoline engines, and gives very 
satisfactorj- results. The fuel is drawn to the engine 

#;;j,-r..-c .e :2ie e agin e. The 
■,>&-:r5t ,-£ ijse icci=g f daring 
•^. i.-^^ trtf irr=:^ closes the 

■ V, -■ .- «•> ,'t^r At tcp of the 

■S:-. . Tae ffMBfjar is fed 


to the vaporizer from a tank placed above the level of the 
engine ; flows first to a reservoir that regulates the flow 
to the vaporizer by the head due to a constant level main- 
tained by an overflow. From the reservoir, the gasoline 
flows to the compartment /, from which it is admitted to 
the chamber g by the needle valve h. The distance the 
needle valve is opened is indicated on the gi*aduated circle i 
by the stationary pointer/. From the chamber g^ the gaso- 
line is admitted to the mixing chamber e by opening the 
valve k^ which is rigidly attached to the inlet valve b. The 
mixing chamber entirely surrounds the chamber g^ so that, 
when the suction of the engine lifts the valve b and thus 
opens the valve k^ the gasoline rises through the opening 
and spreads over a considerable surface. The heated air in 
the mixing chamber vaporizes the gasoline, and the carbur- 
ized air rushes through the valve b and the passage a to the 

When it is desired to use gas with this device, the gas- 
supply pipe is connected to the carbureter at /, so that the 
gas and air mix in the chamber e and the mixture is 
drawn into the engine through the passage a as the suction 
lifts the valve b^ precisely as with gasoline. In either case, 
the charge passes from the inlet valve in the direction of 
the arrows past the throttle, or butterfly, valve ;;/, which is 
operated by the short crank // outside the pipe. A rod from 
the governor is attached to the crank //, so that, as the 
speed of the engine increases, the valve is gradually closed ; 
and, as the speed decreases, the valve is opened, thus regu- 
lating the fuel supply. 

20« Objections to Surface and Filtering: Carbu- 
reters. — In the early days of the gasoline engine, the fuel 
was vaporized simply by having the air drawn over it, or in 
some cases drawn through it in the form of bubbles by the 
suction of the piston. Sometimes, to give an increased sur- 
face for evaporation, a spiral coil of flannel or other suitable 
material, as wicking, was arranged so that it would stand 
partly out of the gasoline, and the air would be drawn over 


.^ _kl A. -■■^* . 


the surface of the gasoline and the wicking. All devices of 
this sort have gone out of general use, on account of several 
important objections. Plain surface evaporation requires a 
very large surface, in order to evaporate the gasoline fast 
enough to supply an engine large enough for average 
demands for power. Again, gasoline is not a homogeneous 
compound ; it is a mixture of light and heavy products of 
petroleum. When it is evaporated from the surface, the 
lighter constituents are evaporated first, and hence in time 
the carbureter contains only the denser portion or stale 
gasolinCy as it is called, which will not evaporate with suf- 
ficient rapidity to supply the air with the amount of hydro- 
carbon necessary for explosion. Another objection to car- 
bureters of this sort is that the rate of evaporation of 
gasoline will depend very largely on its temperature and it 
is difficult to supply the heat necessary to maintain the 
required temperature. The gasoline is cooled by its own 
evaporation, and the heat to make up for this must be sup- 
plied in some way, usually by warming the air before it 
goes into the carbureter by drawing it through a jacket 
around the exhaust pipe of tlie engine. Sometimes the 
gasoline is warmed by means of a jacket around the car- 
bureter, through which is circulated water from the jacket 
of the engine. If the engine speed is at all variable, the 
supply of heat varies. It follows that the gasoline, or the 
air that evaporates it, receives more heat at some times than 
at others, and the richness of the mixture fluctuates accord- 

tj 1 , Advautaii^e of Spray Carbureters. — For the rea- 
s<^ns just stated, the surface and the filtering carbureters 
for internal-combustion engines have been abandoned, aix<l 
their place taken by a large variety of forms of sprayii::^^ 
devices. In these, the gasoline is given to the air in 
form of a jet, or spray, that is drawn from the supply 
the air current. When the air is sufficiently warm, tfais 
spray is evaporated and a fairly constant mixture of air anc? 
ga.soline vapor is thus obtained. 

1_. k : 

8 1? 



The spray carbureter takes up only a small amount of 
space, and hence can be located to better advantage. For 
automobiles and motor boats, this is very important, as the 
space available is small and access to all parts is as neces- 
sary as in stationary engines. 


33, Vaporiser. — In stationary engines, the mixing 
device, or carbureter, is frequently constructed as a part of 
the engine, and is then usually known by some other name. 

oh as vaporizer, or atomizer. A vaporizer for a horizontal 

tionary engine is shown in Fig. 7. The air enters through 

passage shown at a, and the gasoline through the pipe b, 

nected to a gasoline tank located above the engine. 

s inlet valve c is opened automatically on the suction 

Ite of the piston d. The water-jacket that surrounds 

cylinder is shown at e. The gasoline entering at b flows 

the adjustable needle valve/" to the cone-shaped valve 

'Mch is normally held to its seat by a spring, but is 


lifted or pushed forwards during the suction stroke by the 
tappet //. So long as the valve g is seated, the gasoline can- 
not pass it, but when it is open the gasoline flows from the 
small hole drilled in the valve seat, and, passing around 
the conical head of the valve, issues from the spray nozzle i. 
Here it is taken up by the air stream, which passes through 
the constricted passage around the spray nozzle with consid- 
erable velocity, the vaporization being aided by the conduc- 
tion of heat from the engine cylinder through the surround- 
ing metal. The function of the needle valve f is to 
regulate the rapidity with which the gasoline is drawn in 
by the air. The heady of this valve is graduated, to indi- 
cate exactly the valve opening. 

*■ ■ • . • • 

23. Ix>catlon of Gasoline Supply. — ^Usually, it is not 

convenient to locate the gasoline tank above the engine, since it 
ought properly to be buried in the ground to keep it as cool 
as possible and protected from the air. When that is done, 
the necessary head may be obtained by attaching to the 
engine a small pump by which the gasoline is lifted from 
the tank and carried to an overflow cup located above the 
mixing chamber. From this cup the gasoline not taken 
into the engine flows into a return pipe having its inlet 
located at the proper level in the cup, and passes back to 
the tank. 

24. Carbureter With Water-Spray Attadunent. 

A sectional view of the carbureter and mixing chamber as 
designed for the use of gasoline in engines using a water 
spray for cooling the combustion chamber is shown in 
Fig. S. The air supply is so regulated that a certain por- 
tion enters through the passage n, while a sufficient amount 
to vaporize the fuel is admitted through the opening b. 
The tr.e! is supplied by a pump, operated from the engine, 
to a sriiall tank r, in which a constant level is maintained by 
t'-.e overr.ow */. From the resen-oir r, the fuel flows to a 
sniall orir.ce, the opening of which is regulated by the 
r.eei'.e vaIvc c which is provided with a stuffingbox for pack- 
ing. The highest point of the noule/ through which the 




fuel is sprayed into the carbureter, is slightly above the 
Icii-el of the gasoline in the reservoir c. The air-current, 
passing the nozzle f with considerable velocity, creates a 
suction at this point suflScient to draw a certain amount of 
gasoline, in the form of a spray, into the carbureter. After 
passing through several layers of fine-wire gauze at ^, the 

air and atomized gasoline are admitted through the gasoline 
valve h into the mixing chamber a, where they are mixed 
witli sufficient air to form an explosive mixture. This mix- 
ture then passes into the combustion chamber through the 
main inlet valve i. 


26« The opening of the gasoline valve h is con- 
trolled by the governor, in order to proportion the fuel to 
the demands for power. The blade j pivoted on the valve 
nut k engages with an arm on the valve mechanism 
whenever the speed is normal. Under light loads, the gov- 
ernor moves the blade j out of the path of the arm ; hence 
the valve h remains closed and the engine receives air only. 

When working under heavy k)ad, the engine is liable to 
heat up more than under light load. To avoid premature 
ignition imder these conditions, provision is made to add a 
small quantity of water to the mixture of air and gasoline, 
which has the effect of cooling the combustion chamber. 
This water supply is admitted to the mixing chamber 
through the nozzle / regulated by the needle valve w. The 
gasoline vapor passes through the wire-gauze screen g 
before it meets the spray of water. The reservoir c is 
divided by a partition into two chambers, one for gasoline 
and one for water, the water entering through the supply 
pipe, connected to the tank near the top, while the excess 
water is carried off by the overflow pipe «, the amount avail- 
able in the reservoir being regulated by the height of the 
overflow pipe that projects into the reservoir. 

/J 6. Carbureter With IIlt-or-Miss Governed Gaso- 

line Inlet. — A form of carbureter in which the gasoline- 
inlet valve is controlled by a hit-or-miss governing device is 
shown in Fig. 9. The fuel enters the cup a through the 
supply pipe fitting ^, containing an overflow- through which 
the surplus gasoline delivered by the pump returns to the 
storage tank. A float (not shown in the figure), guided in 
the small hole c in the upix^r part of the cup, shuts off the 
supply to the cup as soon as the gasoline reaches a certain 
level. The fuel supply to the engine is shut off by the valve 
d. The main inlet valve c is provided with the washer/, to 
which is connected a sleeve, guided in the casing g and 
sliding on the stem of the main inlet valve e. The governor 
is connected to the fmger //, pivoted on the sleeve of the 
washer /", and when the governor permits the finger to 



engagfe the nut i, the valve e on opening carries with it the 
washer /, which strikes the stem of the gasoline valve/ and 
opens it. A small quantity of gasohne is thus allowed to 
flow from the passage and space above the valve and to 
enter the air passage k through the hole i. The velocity 

of the air-current is such that the fuel, which enters the air 
in a fine stream, is vaporized and with the air forms a 
combustible mixture while entering the combustion chamber 
through the valve e. 

37. Carbureter Witt Hlt-or-Mlss Governed Air 
Inlet. — Another arrangement for admitting and vaporizing 




the fuel for a stationary gasoline engine is shown in 
detail in the vertical section. Fig. 10. This vaporizer does 
not, however, form a part of the cylinder head, but is con- 
nected some distance from it. The gasoline -valve casing a 
is attached to the air-inlet casing d. Gasoline is pumped from 
the storage tank through 
the supply pipe £ into 
the space in tl.e valve 
casing a. A partition 
d, dividing this space 
into two compartments, 
keeps the gasoline at a 
constant level, slightly 
below the top of the 
nozzle pipe*", the excess 
delivered by the pump 
returning to the tank 
through the overflow 
pipe / A threaded 
needle valve /■ regu- 
lates the gasoline ad- 
mitted to the valve cas- 
ing a, while the dial 
val\-e A serves to shut 
off the supply when 
stopping the engine. 

The air enters the pas — 
sage leading to the inlett= 
valve i from the air pipey which taVes the air from the out 
side. At the point where the nozzle -r is inserted, the area o - 
the air passage is reduced so as to create a high velocity of th _ 
air-current at this point, resulting in a strong suction whic~ -= 
drawsaquantity of gasoline from the casing a through a sma~ _ 
hole in the upper end of the nozzle r. The gasoline is thi^ — ; 
atomized by the air-current, and the combustible mixture l. 
.\ir and gasoline vapor passes upwards ioto the combostic^- 
ohaniV^T t. through the val\-e i. It has been fotind that ■* 
Igh velociiy at the point where the gasoline enters tB»^ 


f~■^ - "i 

1 - 




1 ■ 


- ^ 




air-current, contributes largely to the efi&ciency of the gaso- 
line spray. 

3 8. Owing to the strong suction through the inlet valve 
of the arrangement shown in Fig. 10, there is a possibility, 
especially if the inlet- valve spring should become weakened, 
that the inhaling action of the piston may cause the inlet 
valve to chatter, or open to a slight extent, even when the 
exhaust valve is open while no charges are needed to keep 
up the speed of the engin9 under light load. This would, 
of course, result in a waste of fuel, which Tyould be drawn 
into the cylinder, and, forming too weak a mixture, would 
be expelled through the exhaust pipe without being exploded. 
To prevent this, the push rod that opens the exhaust valve 
and is controlled by the governor has an arm or extension 
connected by a horizontal rod to a lever m. When the gov- 
ernor causes the exhaust valve to be kept open, the lever m 
is moved in between the cylinder head and the washer on 
the end of the inlet valve, thus positively locking this valve 
and preventing it from being even slightly opened. 

29. Kerosene Engrine Carbureter. — A sectional view 
of t»ie carbureter of a kerosene engine is shown in Fig. 11, in 
which the exhaust valve is shown at a and the inlet valve 
at by both opening into a passage connected to the end of the 
cylinder. The valve b admits the air required for combus- 
tion ; it is automatic in its action, being opened by the par- 
tial vacuum in the cylinder during the suction stroke and 
closed by the tension of the spring c. The dashpot d at the 
upper end of the valve stem is for the purpose of preventing 
the valve from coming to its seat too suddenly. 

The needle valve e that admits the kerosene to the com- 
bustion chamber is operated by the lever y. The bushing^ 
surrounds the valve and fits into the bracket h that is bolted 
to the cylinder. The nut i with the opening/ is screwed 
Into the bushing^, and furnishes the seat for the needle 
valve e. Between the needle valve and the bushing are 
brass washers ky perforated with small holes, through which 


the oil, entering from a pipe not shown, is forced by com- 
pressed air, which enters through the pipe /. Cooling water is 
supplied to the space around the bushings, entering through 
a pipe not shown, and passing out through the pipe m. The 
joint around the needle valve is made tight by means oi 

the ring «, the packing o and the gland p. The fuel is 
injected into the combustion chamber at the end of the 
compression stroke, when the air admitted during the sue 
tion stroke has been compresseil to about 600 pounds per 

Wiiiarc inch. 


The fuel is injected into the highly compressed contents 
of the cylinder by means of air compressed to about 700 
pounds per square inch, the air being furnished by a sepa- 
rate compressor driven by belt either from the engine or 
from a convenient shaft. The temperature of the air in the 
cylinder at the end of compression is about 1,000° F., which 
is considerably above the temperature required to ignite the 
mixture without the use of any special igniting apparatus. 
The oil is finely atomized by being pressed through the 
numerous small holes in the brass washers k^ thus entering 
the combustion chamber through the nozzle in the form of 
a very fine spray. Owing to the high temperature of the 
compressed air in the cylinder when the fuel is injected, the 
combustion is practically perfect, leaving no residue and 
producing clean exhaust gases. 


30. The conditions under which the carbureter on an 
automobile must operate are more exacting than those found 
in connection with any other gas engine service, for the rea- 
son that an automobile motor runs at all speeds and under 
greatly varying loads, and the carbureter is exposed to great 
variations of temperatures and atmospheric conditions. It 
naturally follows that the simple devices found succesvsf ul on 
stationary engines are by no means reliable when applied to 
automobiles, and even a successful marine carbureter may 
fail to give the best results, when applied to an automobile, 
although any carbureter found successful on an automobile 
will be equally successful in a motor boat. 

31. Requirements for an Automobile Carbureter. 

A successfi\l automobile carbureter must fulfil the following 

1. It must give a practically uniform mixture, whether the 
demand on it is light or heavy, within the range of the speed 
actually attained by the motor. The mixture must be the 
same when the motor is running slowly with the throttle 


wide open, as when going up a hill, or slowly with the throt- 
tle nearly closed, as when coasting or traveling slowly 
on the level, or when running at top speed with the throttle 
wide open. 

2. It must not freeze up in cold weather, through the con- 
densation of moisture from the air and freezing in the mixing 

3. It must not be unduly sensitive to changes in the qual- 
ity of the gasoline, and it must admit of easy adjustment 
for such ordinary variations in density as are likely to be 

4. It must not be unduly sensitive to changes in the level 
of the car, as when climbing or descending a hill, or when 
turning off the road into the gutter. 

5. It must vaporize the gasoline reasonably well when 
starting in cold weather. 

6. It must operate equally well whether the motor has one 
or two cylinders giving intermittent suction, or a larger 
number of cylinders giving practically a continuous suction. 

7. The quality of the mixture delivered must not be 
affected by the vibration of the car. 

8. The carbureter must not be exposed more than necessary 
to the entrance of dirt, and all parts to which dirt is likely to 
find its way must be readily accessible for cleaning. 

It is evident that with so many requirements there is 
no carbureter made that fulfils all of them equally well. 

32. Regrulation of Automobile Carbureters. — Prac- 
tically all carbureters for automobile use are of the constant- 
level type. The gasoline passes from the tank through a 
needle valve to a constant-level chamber, in which the level 
of the gasoline is controlled by a float that acts on the 
needle valve, closing it when the level reaches the outlet of 
the spray nozzle. In this way the rate of gasoline feed to 
the spray nozzle is determined solely by the degree of 
vacuum existing in the mixing chamber, and the velocity of 
the air stream, irrespective of the amount of gasoline in the 
tank. The combined influence of the vacuum in the mixing 


chamber and the velocity of the air stream is to make 
the mixture richer when the motor is running fast and the 
throttle is wide open than it is when the motor is run- 
ning slowly with open throttle, or fast with the throttle 
partly closed. In the first case there is considerable 
vacuum and a high velocity of the air, while in either of 
the other two cases there is less vacuum and a smaller veloc- 
ity of the air. This is because the throttle is located 
between the carbureter and the motor, and not at the car- 
bureter intake, so that, whatever the vacuum may be 
between the throttle and the motor, the vacuum in the car- 
bureter itself is reduced by the throttle valve so that only 
the amount of air required by the engine will be drawn in 
at each stroke. 

The vacuum between the throttle and the motor has no 
effect on the amount of gasoline vaporized; this depends 
only on the speed of the air that is drawn through the car- 

The rate at which the gasoline is drawn from the spray 
nozzle is affected by both the vacuum and the air velocity 
more than it would be by either separately, so that, when 
neither is restricted, too much gasoline is evaporated. It is 
desired to keep the flow of gasoline as nearly as possible 
proportional to the velocity of the air, and in order to 
accomplish this result the newest forms of automatic carbu- 
reters restrict either the velocity of the air stream or the 
vacuum in the carbureter, as the demands of the motor 

33. Vaporizers. — In a larger number of marine 
engines, and in all automobile engines, the carbureter, or 
vaporizer, is a separate device; that is, it is not a part of 
the cylinder head. A simple form of vaporizer is shown in 
Fig. 12. The air in entering takes the course shown by the 
arrow, lifting the trap valve or mixing valve a to a. greater 
or less extent, according to the intensity of the suction. 
The end of the valve has a leather pad that, when down, 
closes the gasoline spray orifice ^, and when lifted, allows 



j ll- 

the gasoline to escape. The pressure that catises the gaso- 
line to rise in b is due partly to gravity, owing to the Icca- 
tion of the reservoir, and partly to the suction of the air 
that picks up the gasoline and breaks it into spray as the 
air-current passes the 
orifice b-. The gasoline 
comes from a tank or 
overflow cup shove the 
level of the mixing 
valve, and its rate of 
flow through the spray 
orifice may be adjusted 
by the threaded needle 
valve c. The air regfu- 
lating valve d may be 
opened or closed by 
hand. This valve ad- 
mils air through the 
ports c, e to dilute the mixture; and by its use, the mixture 
may be regulated to the exact pro- _^_ 

portions required without disturbing 
the needle valve. Regulation of 
this sort may be required for a 
change in the speed of the engine. 

34. Another simple vaporizer is 
shown in Fig. 13. The air enters at 
a, and, as it passes upwards in the 
constricted passage, it impinges ^^ 
sharply on the small flange b of the 
needle valve c, thereby lifting the 
valve to a greater or less extent, 
depending on the velocity of the 
air-ciirrent. In this way, the flow 
of the gasoline is regulated roughly ^^°' '* 

according to the velocity of the air. A stop d is provided 
above the needle valve, to prevent it from lifting so hiff^ 
that it will not have time to close by its own weight at the 



end of the stroki;. The connection to the gasoline supply is 

made at c, and the gasoline rises to the needle valve by the 
pressure due to the height of the gasoline tank. 

35. The vaporiKcr shown in Fig. 14 is used to a consid- 
erable extent in motor boats. Its operation depends on the 

Tacuum produced by the suction ol the engine. The pres- 
stire of the air that enters at a lifts the valve l> against the ' 
pressure o£ iJie spring c, when the engine is taking in a new 
charge. The gasoline enters around the needle valve (/, 
and is sprayed from the passage i- when the valve ^ is lifted off 
its seat. The band wheel / of the needle valve is graduated, 



to indicate the opening. The pointer g can be moved 
to any position and locked there by the locknut //. The 
stop /can be adjusted so as to gfive the desired amount of 
opening to the valve b. The baffle wally deflects the mix- 
ture upwards and causes it to mix more thoroughly without 
reducing the area of the passage k through which it passes 
lo the engine. The baffle wall also serves to prevent any 
liquid gasoline from flowing to the engine. 

JiO. 1 )tsiul vniitii^es of Vaporizers. — Vaporizers like the 
ones shown in Figs. 13 and 14 are much less common now 
than in the past. They arc very wasteful of gasoline, and 
ivquiix^ fre(|uent adjustment to make them supply the 
pnqKM* nnxluR\ One of their most obvious disadvantages 
is that the g^asoline will flow more rapidly to the needle 
valve when the tank is full than when it is nearly empty, on 
account K^i the ditYerence in pressure due to the height of the 
s\ui\ux^ above the valve. The proportion of air to gasoline 
is alsv> noi eniirv^ly constant when the engine speed changes, 
or when the ens;ine is throttkxl. There is a tendency for 
the mixtuiv lo be tov> rich at high engine speeds, since the 
flow of gasoline is not vMily due to the pressure from the 
elevation i^f the ta!\k, but is als«.> due to the partial vacuum 
c\\itii\g in the mixiuii' ohanilx^r and to the velocity of the 
air. Va et\ if no vaouum exist cvl in the mixing chamber and 
;f the \:asv>line hav! r.v^ pressure at the needle valve, the gaso- 
ir/.e Wv^v.'.vl s:r,* K^ crawn into ihe a:r bv the velocitv of the 
\\ \\.\\ \\\\\s *v seen :ha: ther^ an^ four factors that 

atKo: :V,o \^rv^\\>r::v^i\s ot ihe mixture; namely, the head of 
:'\o ci^v^*v,H" *'.*. tV.e tar.k. t'u^ !::: of the needle valve, the 
\,;o;\v*,\*, v.\ ;>e '.vix-v-c v>,a:v.:x^r, the velocitv of the air. ts ivaV.v vUn -.xv, -s :ha: or.'.y ihe last named of these 
•x ; • tav;vv>i sv^uM K^ v^ix^rav.w: or, in other words, that 
t*'o \v*xV't\ x^^ :>x^ v:a>x\ir,c v: sho"\; 'Se :n din?ct proportion 
\o\vu\ V : :>.o ar.\ T>.:> :> Ait-dned in the type 

« k % « 

» X « N 

N « , >'t*v^t-l\xH\ I'^irburxncrs. - 7.":e irne-oriilaritv in the 

^ .V. ' -,^ '.vx ,,0 ;.^ \.r-,;: .•> : ; :>.c level of the gasoline 



in the tank, is eliminated hy passing the gasoline from the 
tank through an overflow cup attached to the carbureter, or 
through a chamber in which the proper fuel level is main- 
tained by a float; so that, when the gasoline rises above the 
proper level, the float closes the inlet valve. This last 
method is used almost entirely in automobiles, and also to 
a large extent in motor boats. 

A simple form of float-feed carbureter is shown in Fig. 15. 
The gasoline enters the carbureter at a from the supply tank, 
and passes through the valve d into the float chamber c. 
The proper level for the gasoline in this chamber ia at or 

very slightly below the top of the spray nozzle d, and 
when this level is reached the float *•, which is hollow and 
very light, closes the valve A. The air entering at / flows 
with considerable velocity through the passage^, and, as it 
does so, a jet of gasoline flows from the spray nozzle d. 
This flow is caused partly by the velocity of the air-current 
and partly by the vacuum induced by thfr piston. Owing 
to the velocity of the air, this jet is immediately converted 
into fine spray in the mixing chamber i, and then passes 



into vapor aljiiost immediately. In order to supply the heat 
demanded by this extremely rapid evaporation, the inflow- 
ing air is sometimes warmed by being drawn throngh an air 
jacket around one of the exhaust pipes, or is taken from the 
warm space between the cylinders below the water-jacket 
In other cases, the air is not warmed before it enters the 
carbureter, but the annular chamber i around the carbureter 
is supplied with either exhaust gases or water from the 
water-jacket of the engine, 

38. Aiitomutlo Float-Feed Carbureter. — A modified 
lorm of the carbureter shown in Fig. 15, known as an auto- 
matic carbureter, is shown in Fig. 16. The gasoline 

Fro. W 

comes from the tank through the opening at a, and the 
prinoiivil air stream enters at !>. The float c closes the 
valve ./ when the lovel of the gasoline reaches the top of the 
spray ui'.r.-lo c. When the engine is running very slowly, 
thi- air ciuoring at /• is all that enters the engine, bot as the 
tliri'ttto is ^llx>n^'^.l nioa- and more, the vacutun in the mix- 
ing i-haniK-r is iiicrt'asi'd and the valve f is opened against 


the resistance of its spring. Air is then admitted in greater or 
less quantity, depending on the amount that the valve / is 
opened, which, in turn, dei)ends on the vacuum, or the 
speed of the engine. This air does not pass the spray noz- 
zle, but is mixed with the carbureted air in the mixing 
chamber^. The effect of the valve f is thus partly to 
reduce the vacuum that would otherwise exist ia the car- 
bureter, thereby diminishing the amount of gasoline sucked 
from the spray nozzle, and also to dilute the air actually 

The two plugs h and / are provided for cleaning the carbu- 
reter of any foreign matter, as dirt and watery that may be 
carried in with the gasoline. As almost all such matter is 
heavier than gasoline and tends to settle to the bottom, it is 
only necessary to unscrew these plugs and cause a little 
gasoline to flow through. The annular jacket/ is connected, 
by pipes not shown, with either the exhaust pipe or the 
water-jacket of the motor, and this serves the purpose of 
supplying the heat required by the gasoline in the process of 
evaporation, thus preventing condensation and freezing of the 
moisture in the air. 

To start the motor, the stem k is depressed, thus opening 
the valve d and permitting the gasoline to escape freely 
from the spray nozzle. In this way a sufficient quantity of 
gasoline is allowed to gather in the intake pipe to produce, 
simply by evaporation, the mixture necessary for starting. 

39. Another type of automatic carbureter that has 
proved very successful is shown in Fig. 17. The air 
enters at a and the gasoline at b. The height of the 
gasoline is controlled by the float c which, as it falls, 
presses on the levers d^ d, and raises the weighted needle- 
valve stem e. When the float rises, the needle valve is 
closed by its own weight. As the gasoline comes from 
the float chamber, it issues from a number of very small 
slots f in the conical head of the spray plug g. This plug 
is drilled upwards from the bottom, and then laterally, as 
shown by the dotted lines, to admit the gasoline to the 



Space beneath a conical cover or head h. The division 
of the entering gasoline into a number of very small 
jets (from 10 to 16) insures a much more rapid and effi- 
cient mixing with the air than when the spray enters in a 
single jet The air coming up from a strikes the head h. 

which is pierced at the top with a number of small holes 
through which the air passes on its way to the throttle 
valve /. The cone h is attached to the stemy* to the other 
end of which is connected a plunger i working against a 
spring in an air dashpot. When the velocity of the air is 


small, practically all the air passes up around the spray plug, 
and through the holes in the head //. When the suction 
increases, however, the air strikes with so much force against 
this head that it is lifted against the resistance of the spring, 
and a portion of the air is diverted and passes around the 
lower edge of the thimble, so that it has no effect on the 
gasoline spray. 

Although this arrangement does not increase the amount 
of air drawn through the passage ^ , it gives the air an easier 
passage when the head is lifted, a smaller proportion of the 
air passes the gasoline plug, and the same result is therefore 
produced. As the carbureted air is divided by the holes in // 
through which it must pass, and the air that passes beneath 
the head flows against the stream of carbureted air on all 
sides, the two streams are very thoroughly mixed, which is 
not always the case in carbureters with automatic air-inlet 
valves. The ptupose of the air dashpot connected to the 
head h is to check the pulsations of the latter when the 
engine has only one or two cylinders. Although the head is 
made as light as possible, it is found that owing to its inertia 
it does not follow perfectly the variations of the air-current 
when the suction is not steady. The effect of the dashpot, 
however, is to cause it to lift to an extent determined by about 
the average intensity of the suction, and to remain in prac- 
tically that position from one impulse to the next. The 
carbureter is primed by unscrewing the valve / a fraction of 
a turn, permitting the gasoline to escape directly into the 
intake pipe a. A spring ;;/ insures the closing of the valve 
when released. The throttle valve i is elliptic in shape, as 
indicated, in order to make it unnecessary to turn it to an 
angle of 90° from the wide-open to the closed position. As 
in the carbureter shown in Fig. 15, there is a jacket n con- 
nected to the exhaust pipe and serving to supply the heat 
taken up by the evaporation. 

In another form of this carbureter, a stop-screw is provided 
to limit the lift of the head, and a needle valve, adjustable 
from the bottom, is provided to restrict the rate of flow of 
the g^oline to the spray i)hii:^. 


40. Another automatic carbureter is shown in Fig. 18 
(a) and (^), the two views being taken at right angles to 
each other. The air enters through the slits a. Fig. 18 {a)j 
in a shutter that can be rotated so as to close them, or give 
them the amount of opening desired. The air passes through 
the openings 6 in the standpipe c that is made small in order 
to give the air considerable velocity as it passes upwards past 
the spray nozzle. The carbureted mixture is then diluted 
by air coming through the automatic valve e, and the final 
mixture passes out through the throttle valve / into a 
branched mixture pipe, which bends upwards and leads to 
the cylinders. The gasoline enters at^, Fig. 18 (b), and the 
float, as it rises, causes the small levers A, A to push 
the needle-valve stem i downwards, thus stopping the flow 
of gasoline. By means of the connections y and ^, warm 
water from the water-jacket of the engine is circulated 
through the jacket /, Fig. 18 (^), of the carbureter. 

The carbureter is primed for starting by lifting the needle 
valve /, Fig. 18 {b). There is no needle valve acting on the 
spray nozzle, but the richness of the mixture is regulated by 
adjusting the openings of the slits a. Fig. 18 (a). This is 
done by means of a shutter surrounding the pipe in which 
the slits are cut. . This shutter has openings cut in it corre- 
sponding to the slits a, and by rotating it the air passages 
are either made larger or smaller. The shutter is controlled 
by the operator through a lever connected to the arm m. 
By partly closing the slits, the relative amount of carbureted 
air is reduced and a larger proportion of air is compelled to 
enter through the valve e, 

41. Carljureters With. Air Inlet Controlled by 
Throttle, — In addition to the automatic carbureters just 
described, there is a large class having the auxiliary air inlet 
rigidly connected to the throttle so that the two open and 
close together. This does not secure strictly automatic 
action, because the speed of the engine varies with the load 
as well as with the throttle opening. Nevertheless, it is 
found in many cases to give exceedingly satisfactory results. 





An early form of such a carbureter, which, however, has 
been little changed, is shown in Fig. 19 {a) and (*), {a) being a 
top view and {b) a sectional side view. At a is shown the float 
chamber; at ^, the spray nozzle; and at r, a choking device 
equivalent to a needle valve, except that its end is blunt 
instead of pointed; it is carried by a screw of coarse pitch, as 
shown, and is raised or lowered to increase or retard the 



flow of gasoline from the nozzle by turning the screw by 
means of the lever d. The principal stream of air is warmed 
by passing around the exhaust pipes, and enters the annular 
chamber e by the pipe ^, and, following the direction of the 
arrows, it is drawn past the spray nozzle d and up into the 
branch pipe /, which leads directly to the inlet valve cham- 
bers of the engine cylinders. The auxiliary stream of ai-x" 
enters by the slot // in the tube /. Inside this tube is a slot - 
ted shutter or sleeve /, with the right-hand end closed an ^^ 
connected to the stem /. When the shutter is moved to tl»-^ 
left or right, it will partly cover or uncover the slot A, aa- <3 
at the same time, by moWng to the left, it partially obstruents 
the passage both of the carbureted air and of the auxiliar""^ 
stream of air before they pass into the pipes i6, /. 




48. In another carbureter, a by-pass controlled by a 
throttle furnishes ,the auxiliary or diluting air stream. This 
throttle is connected to the main throttle, but there is also a 
valve controlling the entrance of the air to the spray chamber. 
This valve, by lifting when the velocity of the air increases, 
tends to keep the suction in the spray chamber more nearly 
constant than would otherwise be the case. Fig. 20 shows 

two sectional views of such a carbureter, the two views 
being taken at right angles to each other. The intake for 
both the main and the diluting air streams is shown at a. 
Fig. 20 [ii). The spray chamber is greatly contracted about 
the spray nozzle b, to give the air a high velocity, in order that 
the gasoline may be drawn freely through the spray nozzle. 
The air valve c is shown wide open. The auxiliary air stream 
passes up through d, Fig. 20 (a), past the butterfly valve e, 
which is controlled by the links and levers at f, attached to 
the main throttle^, Fig. 20 {b). The passage of the gasoline 
from the float chamber to the spray nozzle is controlled by 
the needle valve h, which is regulated by the operator. 


I 17 

43. Central-Peed Carbureters. — The carbureter shown 
in Fig. 21 has several advantages over the one shown in 
Fig. IG. Instead of the spray chamber a and float chamber b 

being entirely separate, the spray chamber is located inside 
the float chamber. Br reason of this arrangement, the car- 
bureter is not afEected by tilting, which might cause the 


gasoline to overflow from the spray nozzle or to require con- 
siderable suction to lift it to the top of the nozzle. Also, the 
needle valve Cy controlling the entrance of the gasoline to 
the float chamber is closed by the weight on its stem, instead 
of directly by the annular cork float d^ whose function it is 
to raise the weight through the action of the lever e. As 
the arm of the lever connected to the float is much longer 
than that acting against the weight, a much more positive 
closing of the valve is secured than if the float were to act 
directly on the valve. 

In this device, the throttle is made a part of the carbureter, 
and is operated by the lever arm /at the top. The princi- 
pal air stream enters at the bottom through the wire-gauze 
dust screen^ and passes upwards past the spray nozzle. 
The auxiliary stream enters by the automatic inlet valve A, 
which opens downwards against the spring i. This valve is 
composed of a fiber disk, with a brass bushing guided by the 
stem of the screw j\ The threaded bushing k may be 
adjusted to vary the tension of the spring i. The spray 
opening is regulated by the needle valve /. The carbureter 
is primed for starting by raising the stem m of the needle 
valve. As the weight is attached to this stem by means of a 
screw thread as shown, the weight may be screwed up or 
down, and the level at which the float will act on the gaso- 
line valve will be altered. For example, if it is found that 
the float does not close the valve until the gasoline has 
reached too high a level, it may be adjusted by screwing the 
weight upwards on the stem, which will permit the valve to 
close when the float stands in a lower position. 

4:4« A section of a type of carbureter used in both auto- 
nniobile and marine practice is shown in Fig. 22. It differs 
from those previously shown in a number of particulars. 
The gasoline enters at a and the air at by which in the car- 
bureters previously shown would naturally be the outlet. 
The air therefore flows downwards past the spray nozzle, 
instead of upwards as is more usual, and passes through the 
throttle valve and out at c. The float d is shaped so that it 



goes on each side of the mixing chamber. It is secured to a 
lever pivoted at the right, and rising closes the needle valves. 
In the passage b is an automatic air-inlet valve _/i closed by 
s of a spring g, as shown. This valve does not entirely 

close the air passage when it rests against its seat, hut ^ 
the bottom is left an opening through which is suppli^' 
the necessary air for keeping the motor in operation uni3-^ 
the slowest running conditions. As the suction increas*^^' 
this valve opens against the spring g, thereby admitting" * 
larger quantity of air. 

The gasoline passes directly from the float chamber to tS^ 
spray nozzle //, the opening of which may be regulated by 
the needle valve ('. As the opening of this nozzle is exactlj' 
in the center of the float chamber, the carbureter is not 


affected by being tilted. The throttle valvey is opened and 
closed by means of the lever k ; the mixture of air and gaso- 
line passes through in the direction indicated by the arrow. 
Adjustment of the automatic air valve / is obtained by 
modifying the tension of the spring g^ by screwing up or 
unscrewing the shouldered stem /, which extends through 
the valve y* to guide it, but is not attached to it A drain 
cock in is provided at the bottom of the float chamber, for 
the purpose of empt)dng or for drawing off water that may 
have got into it. 

In starting the engine, the float d is depressed by means 
of the lever «, which depresses the pin o. This allows the 
level of the gasoline to rise above the nozzle A, when enough 
gasoline enters the air passage to start the engine. This is 
known as ^priming device. 


45. A carbureter may deliver too rich a mixture or too 
weak a mixture, at all speeds within the range of operation 
of the engine. More often, however, a mixture will be rich 
at certain speeds, high or low, and either normal or, possi- 
bly, too weak at other speeds; or it will be weak at high or 
low speeds and normal or too rich when the speed is 
changed. Owing to the large number of types of carbu- 
reters, no definite rules that will apply to all can be made for 
their adjustment. If the printed instructions of the maker 
are at hand, they should be followed. If these should fail 
to give the desired result, an observance of the following 
general principles may aid in correcting the trouble. 

1. A non-automatic carbureter will tend to take propor- 
tionally more gasoline at high than at low speeds. If 
adjusted correctly for low speeds, it will be wrong for high 
speeds, and vice versa. 

2. A needle valve acting on the spray nozzle does not 
produce automatic regulation; it reduces or increases 


the gasoline feed in substantially the same ratio for all 

3. A fixed shutter over the air intake does not produce 
automatic regulation. By partly closing it, the suction in 
the spray chamber is increased and the amount of air sup- 
plied is reduced, thereby increasing the richness while 
reducing the volume of the charge. 

4. To obtain a uniform mixture with a carbureter that 
is not automatic, the gasoline feed at high speeds must be 
restricted, or the air must be allowed to enter more freely, 
to diminish the suction in the spray chamber. Some car- 
bureters are arranged to by-pass a portion of the air around 
the spray chamber at high speeds. If the by-pass valve 
controlling this action is connected to the throttle, the type 
of carbureter will be like those shown in Figs. 19 and 20. 

5. In an automatic carbureter, opening the needle valve 
or reducing the air-intake opening will give a richer mixture 
at all speeds. 

6. In an automatic carbureter, reducing the spring ten- 
sion on the auxiliary, or diluting, air valve will permit this 
valve to open wider, especially at high speeds, and will 
therefore make the mixture weaker at high speeda The same 
principle holds good regarding the spring tension on such a 
device as the head or thimble, shown in Fig. 17, that per- 
mits a portion of the air to pass around the spray chamber. 
Increasing the spring tension makes the mixture richer at 
high speeds. 

7. A weaker mixture may be obtained at low speeds tj 
increasing the spring tension on the automatic or auxiliaiy 
valve and enlarging the main air intake ; or it may be 
obtained by increasing the spring tension and partly dos- 
ing the needle valve. The latter arrangement will not give 
as full charges as the other, as the resistance to the ingoing 
charge will be greater, but if the carbureter is large for the 
engine it may give better vaporization on account of the 
higher air velocity past the spray nozzle. 

8. If at high speed richer charges are desired, thd thro^' 
tling effect due to increasing the spring tension on tlw 


automatic valve may be offset by increasing' the opening of 
the main air intake. The needle valve also should be opened 
further, to avoid the necessity of restricting the automatic 
valve unduly. At low speeds, the increased openings of the 
main intake and the needle valve will neutralize each other 
as regards the proportions of the mixture. 

9. If the automatic valve is provided with a stop, its 
effect will be to render the carbureter non-automatic at 
speeds above those at which the automatic valve comes 
against the stop. For this reason, reliance should be placed 
on the spring where possible, rather than on the stop. The 
chief function of the stop should be to prevent the valve 
from opening under sudden pulsations so far that, by reason 
of its inertia, it cannot close promptly. 

10. A slightly weak mixture bums faster than a normal 
or a rich mixture. This, therefore, is the best mixture for 
high speeds. When, however, the motor is working under 
a heavy load, a slow-burning mixture is better, as it main- 
tains a higher pressure on the working stroke. The ideal 
carbureter adjustment, therefore, should give a normal mix- 
ture, or one very slightly rich, at the slowest speeds, and a 
weaker mixture at high speeds. 

11. Occasionally, a change in carbureter adjustment is 

made necessary by a change in weather or in the quality of 

the fuel. Such changes are properly made in the main air 

or needle-valve openings, since the changes must be the 

same for all speeds. 

12. In order to have correct adjustment, the gasoline 
level in the float chamber must be at or slightly below the 
spray orifice. 

46. Adjustment of Ne^v Automobile or Marine Car- 
bureter. — In adjusting a new carbureter, the first thing to 
^0 is to see that the gasoline level is at the right height, 
^hich it probably is. If not, examine the float to see 
* that it is working properly and is set correctly. Next see 
^t the igniting device produces a good strong spark, and 
^^ox follow the instructions of the maker regarding the 


setting of the needle valve, main air intake, and automatic 
valve. Prime the carbureter freely, and start the engine. 
Run it throttled to about half speed at first, with suitable 
spark lead, and gradually reduce the opening of the needle 
valve, a little at a time, until the engine shows signs of run- 
ning weaker. Then open it to the point where the engine 
runs best. If the engine starts, but will not keep on 
running, it is getting either too much or too little gasoline, 
probably the latter. The former will be indicated by black 
smoke in the exhaust, and probably a very loud exhaust due 
to slow combustion. If there is no black smoke, but the 
motor will not run, try increasing the needle valve opening, 
a little at a time, until the motor runs steadily, after which 
adjust as before. 

Now open the throttle a little, and note the result, as the 
engine runs up to or a little beyond its maximum speed. If 
it weakens, it is probably getting too much gasoline. Relax 
the spring on the automatic valve, and try again. Watch 
for black smoke, but remember that this appears only when 
the excess of gasoline is considerable. If necessary, open 
the needle valve and readjust the main air intake. Try also 
closing the throttle until the motor barely runs, retarding 
the spark, and note how quickly it responds as the throttle 
is opened. A little further experimenting along the lines 
just indicated will result in an adjustment suflBciently cor- 
rect to allow the engine to be run in regfular service, after 
which it is comparatively easy to discover what changes will 
produce the best mixture. 



iQtNition systems 


1. If the ends of two wires forming part of an electric 
circuit are brought in contact, thereby closing the circuit, 
and then quickly separated, a bright spark will be produced 
as the contact is broken. This phenomenon underlies the 
operative principle of what is known as the make-and- 
break system of Igrnltlon, with which it is necessary first 
to complete the electrical circuit through the spark-producing 
mechanism, or Igrnlter, and then break the circuit to obtain 
a spark for igniting the charge. In stationary gas-engine 
practice, the simplest kind of igniter uses city lighting cur- 
rent, with an incandescent lamp in series in order to pre- 
vent the current from being too strong, and consists simply 
of a mechanical device for making and breaking the circuit 
in the combustion chamber at the proper moment. 

2, In Figs. 1 and 2 is shown an elementary make-and- 
^ak ignition device. In Fig. 1, a: is a shaft turning at 
^'^•half the speed of the engine, or, if the engine is of the 
^o-cycle type, it turns at the same speed, and may, in fact, 
°^ the engine crank-shaft itself. On this shaft is a cam b, 
'leqnently called a snap cam, that bears against a plunger 
^» held in contact with the cam by the spring d. The upper 
^^ of this plunger has an adjustable head ^, against which 

^^^Mr^hM Jy Intematianal Textbook Company. Entered at Stationers^ Hall, London, 

1 18 



bears a finger/, secured to a rocking stem g. This stem^ 
passes through the wall of the combustion chamber, and 
near its inner end it has a ground flange to prevent the gases 
from blowingpast it. The innerend 
is prolonged in the finger k, that 
makes contact with an insulated stem 
1 /', to whose outer end one of the wires 
' of the electric circuit is attached. 
The light spring^/' holds the finger k 
against the stem i, except when the 
two are separated by the pressure 
of the head e against the finger / 
In Fig. 3 is shown a view of the 
P^rts /, g, h, and i taken at right 
angles to the view in Fig. 1. Because 
the greater tension of the spring d 
overcomes tliat of the spring/, the 
contact points are normally out of 
contact except when the plunger is 
pushed upby the cam. The adjustment of the head e is such 
that after contact has been made it leaves the finger/^ and 
continues its upward motion a short distance, so that, when 
the plunger snaps off from the cam, the head strikes the 
finger a smart blow, thereby causing an abrupt separation of 
the contact points. By reason 
of this abntpt separation, the 
contitct points are saved from t 
being burned or fused by the 
arcing of the current that would 
otherwise occur. In spile of ^ 
this precaution, however, the 
contact piiints deteriorate rap- 
idly frrim the intense spark; 

conscfjuently, an electric-light current is used for ignition 
only when dilute g;is is use.! — such as producer or blast- 
furnace gas, hi lib nf whii-h ignite with difhculty — or in large 
engines, where reliability of ignitinu is of more consequence 
than the burning of the contact points. 



3. Figf. 3 sliows an igniter plug for a stationary engine 
as it appears when removed from the cylinder head. To 
avoid corrosion and consequent sticking in the cylinder 
head, the plug a, which enters the head, is usually made of 
brass. It contains the stationary electrode b and the mov- 
able electrode c, both being fitted with platinum tips at the 
points of contact. The fixed electrode b is insulated from 
the plug by means of bushings made of porcelain, lava, 
mica, or some similar insulating material. If of porcelain 
or lava, they are made 
ti£fht against the pres- 
sure of the explosion by 
asbestos- packing wash- 
ers between the faces of 
the insulators and the 
collar of the electrode, 
the countersunk ptir- 
tions of the plug in 
which the bushings are 
fitted, and the nut d 
that holds the electrode 
in place. The movable electrodes has a long stem e passing 
through the plug, and has an interrupter lever /"fitted loosely 
on it. A stop-lever^ is held firmly on the stem e by means 
of a cotter h, passing through the lever and stem, and a 
spiral spring ( fastened at one end to the interrupter lever/" 
and at the other end to a pin passing through the extreme 
end of the electrode stem e, the spring being twisted so as to 
cause its tension to press the blade of the interrupter lever/ 
against the arm of the stop-lever^, A stop-pin / attached 
to the inner end of the igniter plug limits the space between 
the two points of contact when the electrodes separate. 

The spark is produced by rotating the interrupter lever/ 
about the axis of the stem f to a point beyond that at which 
the igniter points b and c are in contact. When these points 
meet, the stem r ceases to rotate and the lever /and arm. ^ 
are separated, while some additional tension is also put in 
the spring r. When the lever / is released, the spring i 



causes the lever to retnni, 
striking the arm g a sharp blow 
and causing- the igniter points 
to be quickly separated, thus 
producing the spark. 

4. While, in application and 
principle of operation, the 
make-and-break igniters used 
on diflEerent marine engines are 
very much alike, they are very 
dissimilar in details of construC' 
tion. A front elevation and a 
horizontal section of one form 
of igniter used on a four-cycle 
marine engine are shown in 
Fig. 4 {a) and (*). The igni- 
tion mechanism is operated by 
means of an eccentric a that 
actuates the igniter rod i. The 
latter is attached to the arm c 
of the movable electrode d by 
means of a trunnioned block t 
held in place by the yoke or 
igniter hammer f hsA. the 
springs^audA, the latter imme- 
diately under the head-end j oi 
the igniter rod, as shown. The 
igniter trip, or latch, k is piv- 
oted on the igniter-rod end j. 
As shown in Fig. 4 (*), the 
arms c are pinned to the outer 
end of the stem of the movable 
electrode d, whose contact arm 
/ is provided with a ground bev- 
eled scat or taper fit in the 
ignilcrbonnet m. The station- 
ary electrode « is insulated from 


the igniter bonnet by means of mica disks o fitted into recesses 
in the igniter bonnet and held in place by a washer and 
nuts /. On the contact arm / and on the inner end of the 
stationary electrode ;/ are contact points, shown dotted in 
Fig. 4 {a), of platinum, nickel steel, or other material that 
does not oxidize readily under heat. 

When the eccentric a moves in the direction of the arrow, 
the igniter rod b will rise, carrying with it the yoke or ham- 
mer y*, compressing the springs g and //, and lifting the 
igniter block e so as to carry the inner arm of the movable 
electrode into contact with the contact point of the station- 
ary electrode and thus close the circuit Further upward 
movement of the igniter rod serves simply to increase the 
tension of the springs g and //, so that, when the horizontal 
arm of the latch k comes in contact with the igniter pin y, 
and the latch k is thereby thrown away from the hammer 
yoke yj the latter will descend quickly on being released. 
The rapid descent of the hammer / causes a sharp blow to 
be struck on the igniter block e^ resulting in a quick break of 
the contact between the movable and stationary electrodes, 
and thus producing a spark that ignites the charge. 

6. To run an engine at varying speeds, it is necessary, in 
order to obtain the best results, to modify the time of ignition 
to suit the speed, making the time earlier for high than 
for low speed. It is also necessary to modify the time of 
ignition, according to the load the engine is carrying, if the 
engine is regulated by throttling. In other words, with a 
given speed, a charge will bum faster if highly com- 
pressed, as when a full charge is taken, than if only 
slightly compressed, as it may be if the charge has been 
much throttled. For these reasons, all automobile engines 
and a great number of launch engines are provided with 
means for varying the time of ignition. The time of 
ignition can be varied with the primary ignition device 
shown in Fig. 1, by pivoting the guide ^ at / and swinging it 
a little to the right for a later spark, and to the left for an 
earlier spark. 



6, With the igniter mechanism shown in Fig. 4, the time 
of ignition is regulated hy means of an adjusting lever r 
operated by a horizontal rod s. Forward motion of the 
lever r raises the threaded igniter pin y; while a rearward 
movement lowers it, thus advancing or retarding the time 
of tripping the latch k and hence the time of ignition. 

7. Of many simpler devices than this, it is necessary to 
mention but one type, operated by a straight spring-returned 
igniter rod that, in turn, is actuated by a cam of any desired 

shape. The igniter rod passes through a flat rocker lever. 
There is a flat washer on each side of the roclcer-arm. 
with springs hold by collars or threaded nuts above and 
below. In action, the igniter rod rises, and the rocker- 
arm, washers, and springs assume the position shown in 
Kig. 5 ((?) when the contact within the cylinder is made. 
The rod continues to rise until it is tripped at the time of 
i^ition by any suitable means. The rod, lever, springs, and 
washers then assume their normal positions, the igniter points 



separate, and ignition takes place. Fig. 5 (d) shows a modi- 
fied form of this simple ignition mechanism. 

In a large number of two-cycle marine engines on 
the market, the insulated electrode is not mounted in a 
removable bonnet with the moving electrode, the usual con- 
struction being to have the insulated electrode inserted 
through the cylinder head. 

8, With a low- voltage current, such as that derived from 
a pnmary battery, a spark coil must be employed to produce 
the necessary electric tension or voltage for the spark. 
When a battery and spark coil are employed, the abrupt- 
iiess of the break between the contact points serves to 
increase the intensity of the spark, it being largely propor- 
tional to the sharpness of the circuit rupture. In Fig. 6 is 
shown an elementary wiring 
diagram for a primary igni- 
tion circuit, with the direc- 
tion of the current shown by 

^'Tows. When the timing 

^'^ni a brings the points ^ and 

^ into contact, the current 

flows from the battery d 

through the switch e (when 

^Josed), the spark coil /, the 

insulated electrode ^, the 

locking contact finger //, and the grounded contacts /,/, back 

^o the battery. The grounded connections /, t may be made 

^0 the frame of the machine, or any other convenient metallic 

^turn may be used. 


&• The mechanism of the makc-and -break system of igni- 
tion requires a considerable number of moving parts that arc 
naore or less objectionable in an automobile engine, and the 
^ority of automobile builders prefer to use what is known 
2S the jump-spark system of ignition, in which the primary 
current is converted by. an induction coil into a secondary 




current of sufficiently high tension to cause a spark to jump 
an air gap. With this system, a revolving contact timer is 
employed in place of the snap cam b shown in Fig. 1. As 
there are no other moving parts, the virhole apparatus is 
extremely simple. 

10. In the diagram. Fig. 7, are shown the essential ele- 
ments of a jump-spark system of ignition. Here a is the 
battery, ^ is a switch for opening the primary circuit when 
it is not in use, and ^ is a revolving timer turning at one-half 
the speed of the crank-shaft, if the engine is of the four-cycle 









Fn;. : 

type. The timer in the elementary apparatus shown consists 
of an insulating ring d mounted on the shaft and having 
dovetailed into it a copper or brass segment ^, in electrical 
connection, by a screw or otherwise, with the shaft y. A 
plate g is mounted loosely on the shaft, so that it does not 
turn with it, but may be rocked about it through a suitable 
arc, say 4r>'^. Mounted on this plate, and insulated from 
it, is a brush //, that bears against the insulating ring and 
makes contact with the metal segment at each revolution of 
the latter. The primary winding of the spark coil is 
represented by /, and / is the groimd on the engine. 
A trembler h, similar to an electric buzzer, is provided so 
that the current may be rapidly interrupted. The trembler 


is exactly like the interrupter or vibrator of a Ruhmkorff 
coil, and its purpose is both to interrupt the current more 
rapidly than could be done by the timer and to produce a 
stream of sparks instead of a single spark only. 

11. The course of the current is from the positive pole 
of the battery to the trembler, then to the primary winding of 
the spark coil, the engine frame y, through e to the brush of 
the timer, when contact is made, and finally through the 
switch b to the negative terminal of the battery. The negative 
terminal of the secondary winding of the coil is connected to 
the battery terminal of the primary winding, and the posi- 
tive secondary terminal is connected to the insulated mem- 
ber of the spark device, or spark plug:, from which, after 
jumping over the gap /, the current returns to the coil by 
way of the engine frame/ and primary winding. When the 
circuit is closed by the timer, a stream of sparks passes 
between the spark points /. For use with small, high-speed 
motors, the coil vibrator is frequently omitted, and a snap 
or vibrating form of timer is used that gives a quick break 
but only one spark. 

12. As in the RuhmkorfiE coil, the primary winding is 
provided with a condenser ;//, which serves the double pur- 
pose of increasing the abruptness of the circuit rupture, 
thereby increasing the intensity of the secondary spark, and 
of absorbing the current that otherwise would produce a hot 
spark at the trembler contacts, and soon bum them out It 
will be remembered that the function of a condenser is to 
absorb the extra current induced in the primary coil at the 
moment of rupture. Under the primary system of ignition, it 
is precisely this extra current that produces the useful spark 
in the engine; but in the secondary system, this extra current 
is objectionable, because it dies down so slowly that it fails 
to induce a sufficiently intense spark in the secondary coil. 

The change of the time of ignition is accomplished for 
difEerent speeds by rocking the plate g to the right or left by 
means of the rod », so that contact is made by the timer 
early or late in the revolution of the shaft. 






13. With small engines, the source of the ignition ctirrent 
is commonly a battery, which may be primary or secondary 
according to conditions. If the engine is stationary, the 
battery is commonly an Edison- Lalande or other oxide-of- 
copper battery. For marine motors, storage batteries are 
sometimes used, and sometimes also the oxide-of-copper 
batteries, but the most common source of current is the 
dry cell, which is now made in certain forms with very high 
efficiency and long life. For automobiles, the battery is 
either of the primary dry-cell type just mentioned or of 
some special type of storage battery. 

14. When dry primary cells are used, the number neces- 
sary will depend on the winding of the spark coil and the 
size and condition of the cells. Some coils wotmd for dry 
primary cells require a higher voltage than others, and the 
internal resistance of the cells has also a considerable influ- 
ence. Dry primary cells can now be obtained that, even in 
the small, or 6-inch size, i. e., measuring 6 inches in height, 
will, when fresh, test over 25 arnperes on short circuit 
Of these fresh cells, generally four or five, sometimes even 
three, will be found sufficient; but, as they approach exhaus- 
tion, one, two, or three more must be added. The first cells 
of the set are thrown away when spent, and fresh ones put in 
their place, while the last cells are still useful. A good 


rangement is to have two sets, of from five to eight cells 
ich, arranifed so that current may be taken from either set 

While four dry-battery cells when new will ignite the 
lai^, it is customary to use from six to eight cells. With 
-oper care and adjustment to the proper length of contact 
>r make -and- break ignition, a set of cells in a motor boat 
ill sometimes last two seasons or more, while dry cells acci- 
intally short-circuited and left 2 or 3 hours will be ruined. 

No matter what type of battery is used, in motor boats 
r elsewhere, the cells should be kept dry, and a reserve set 
oould always be kept on hand for use in case of failure 
rom any cause, A very large proportion of drifting boats, 
Dmetimes in dangerous places, are disabled as a result of 
xhausted batteries. 


16. The only care a primary drj- battery requires is to test 
t occasionally with an ammeter to determine the condition of 
te cells. This should be done cite cfU at a time, with a 
wket ammeter such as is shown 
a Pig. 8. The instrument is 
ised by touching the part marked 
arhon to the carbon (positive) 
erminal of the battery, and the 
nsulated cable a to the zinc 
negative) terminal, which short- 
inniits the cell. The particular 
nstrument shown indicates both 
Hits and amperes, the latter '^^^illSlit^ 
■nly when the button b is pressed, 
'he button should be pressed for "'■ 

1 instant only, barely long enough to allow the needle to 
)me to rest, as the battery is very rapidly depleted by 

Occasionally, the battery box used on automobiles for 
■Iding the cells should be opened and the nuts of the bind- 
% posts tried with the fingers to see that they have not 


worked loose. It is well also to examine the flexible bat- 
tery connectors, since, if these are of the ordinary ready- 
made sort, they are probably too short to have sufficient 
flexibility unless the battery cells are packed very tig-htly, so 
as to entirely prevent them from shaking. Any vibration 
of the cells will, in time, break the connectors. As this gen- 
erally occurs inside the insulation, it is a difficult thing to 
locate, and it is best detected by substituting a fresh con- 
nector for any one that, when tried by bending it in the 
fingers, appears to be broken. 

16, Good battery connectors may be made up from 
No. 16 flexible lamp cord in 8-inch lengths. The cord is 
imtwisted for the purpose, and each length makes two con- 
nectors. The ends of the cords are scraped for a length of 

about 1 inch, and the bairb wire 
twisted and doubled on itself. The 
wire is then slipped through a ter- 
minal or copper connector of the 
form shown in Fig. 9, the bare end 
being run through the stamped 
^^^" " loop a. The loop is then ham- 

mered flat, the wire doubled back upon itself, and the clips 
by b bent over the insulated part of the wire with a pair of 
pliers. The wire is then coiled around a lead pencil. 

If the binding posts on the battery cells show a tendency 
to work loose, the nuts may be locked with nuts taken from 
discarded cells. If, however, the wire connections are flex- 
ible, such as those just described, and the cells do not shake 
about, there will be little tendency on the part of the nuts 
to work loose. 

17. In testing a primary battery, it should be remem- 
bered that on standing the cells will recuperate sufficiently 
to show on test a strength apparently sufficient for a consid- 
erable mileage; but if they are nearly discharged they will 
go down again in a few miles and cause the engine to miss 
explosions apparently without reason. If there is reason to 


think that the battery is nearly spent, the cells should be 
tested after the car has been run 5 or 10 miles. If they 
show less than 5 amperes on short circuit they are not worth 
keeping, unless the spark coil is very efficient Since a 
primary battery will recuperate somewhat on standing, the 
possession of two sets of cells, both of which are nearly 
exhausted, enables the operator to keep the engine going 
for some time by switching alternately from one battery to 
the other. When that expedient fails, the two sets may be 
recoupled in series and used a little longer. 


18. The majority of the storage batteries used for igni- 
tion purposes are similar in construction to those used for 
vehicle propulsion, but of smaller capacity; but there are 
also a few dry storage batteries in which the acid solution is 
mixed with silicate of soda, by which is produced a sort of 
jelly that is not subject to the risk of spilling. When liquid 
cells are used, they are, of course, sealed, and have a rubber 
screw plug in the top with a small vent through it for the 
escape of gases produced in charging. By unscrewing the 
plug, a syringe can be introduced to take out a portion of 
the liquid for the purpose of testing its density with a 

The storage-battery equipment of an automobile almost 
mvanably consists of two sets of two cells each,but occasionally 
three cells are used. The negative terminals of both sets 
are connected together, and the positive terminals lead to 
independent terminals on a two-throw switch, so that either 
battery may be used at will, while the other is held in 
reserve until the first is discharged. 

19. When a storage battery Aveakens to such an extent 
that explosions are missed, it can no longer be xised until 
recharged, for storage batteries do not recuperate when put 
out of service and allowed to stand. A storage battery dis- 
charges itself slowly, and when it is partly discharged it 


loses its strength much more rapidly than when Mly 
charged. For this reason, a storage battery should be used 
continuously until it is discharged before the other battery 
is put into service. A storage cell is discharged when its 
voltage on open circuit has dropped to 1.8 volts. Down to 
this point the voltage ^vill drop rather slowly, but with 
increasing rapidity as the end is approached, and from 1.8 
the voltage falls off with extreme rapidity. 

A storage battery is tested by testing its cells individually 
with a voltmeter, an ammeter being useless for this pur- 
pose, and it should be recharged as soon as the voltage of 
either cell has fallen to 1.8. It i% in fact, best to recharge 
a little sooner than this, in order to avoid being unexpect- 
edly stranded, and for this purpose the battery should be 
tested regularly once in from 100 to 200 miles. ' It is well also 
to test the battery in reserve at the same time, to see how fast 
it is losing its charge. The voltmeter used should also be 
tested occasionally by comparison with an instrument of 
known accuracy, else its reading is likely to be misleading. 

20, In places where no direct current is available, but 
where alternating current can be obtained, storage batteries 
for ignition purposes or for use in electric vehicles may be 
charged through the use of what is known as a mercury- 
vapor converter, a comparatively simple device for con- 
verting alternating to direct current without using vibratory 
or rotating mechanism. 


21. The following are general directions for the care of 
ignition storage batteries: The electrolyte or acid solution 
should always cover the tops of the plates to a depth of 
about \ inch. Replace with fresh solution any loss by spill- 
ing, but use distilled water where the loss is due to evapora- 
tion. Use only chemically pure sulphuric acid. The pro- 
portion of acid to water is about 1 to 6, by liquid measure, at 
G0° F. Use a glazed-stone vessel for mixing, and add the acid 
to the water very slowly^ while stirring with a glass or hard- 

S 18 



rubber rod, the purpose being to distribute evenly through- 
out the mixture the heat generated as the acid and water 
mix. The water must never be pourediiito the acid^ for the 
reason that, being lighter than the acid, it would flow 
quickly over the top of the acid, and the rapid generation of 
heat would quickly transform the water into steam and 
cause both water and acid to be thrown violently from the 
containing vessel. When the electrolyte is cool, 
it should be tested with a hydrometer, such as 
that shown in Fig. 10, which shows a style of 
hydrometer designed for use in liquids heavier 
than water and one that is particularly adapted 
for use in testing the cells of automobile bat- 
teries. The hydrometer a is placed within the 
glass tube ^, and by means of the rubber bulb 
sufficient electrolyte can be drawn i;ip to float the 
hydrometer. Enough liquid is drawn up to fill 
the tube up to the mark d ground on the glass, 
and the reading is taken at the point where the 
floating tube a emerges from the liquid. On 
test, the hydrometer should read between 20® 
and 25° Baum6, or 1.1 02 to 1.2 specific gravity. 
When the battery is fully charged, the electrolyte 
should be about 30° Baum6 or 1.26 sp)ecific grav- 
ity. If the specific gravity is low, remove some 
of the liquid with a rubber syringe bulb and add 
a stronger solution, not exceeding 1,4 specific 
gravity or 41° Baumd. If too high, add distilled 
water until the proper density is reached. 

When setting up new cells, pour through the 
holes in the cover, by using a funnel of glass or hard rub- 
ber, sufficient sulphuric-acid solution to cover the plates fully, 
and charge the battery immediately. 

Whenever the battery is to be charged, remove the vent 
plug from each cell to allow the gas to escape. Care should 
be taken not to bring a naked flame near these openings 
while charging, as the gases given off are hydrogen and 
oxygen, and are highly explosive when mingled. 


PlO. 10 


The completion of the charge is indicated, first, by a fine 
boiling or discharge of gas sometimes called ^assin^^ which 
gives to the liquid a kind of milky color, and, second, by the 
voltage, which must be near to 2^ volts per cell, the test 
being made during the charge. If a voltmeter or hj'drom- 
eter is not available, the charge should be continued until 
each cell has been gassing, or bubbling, about 20 minutes. 
Do not prolong the charge beyond this limit Cells should 
never be allowed to stand discharged, but when discharged 
should be recharged immediately. 

33. Direct current only, never alternating, should he 
used for charging. Be sure to connect the positive wire of 
the charging line with the positive pole of the battery, as 
otherwise the battery may be ruined. If there is no volt- 
meter at hand to determine which wire is positive, attach a 
piece of lead to each wire, and immerse both in a small 
quantity of the electrolyte, but without allowing them to 
touch each other, when the positive piece will turn brown. 

Always place sufficient resistance between the positive 
terminal of the charging line and the positive pole of the 
battery to make the voltage, as measured between the 
charging terminals, when the battery is connected, not more 
than 25 per cent, greater than the rated battery voltage, or 
5 volts for a 4-volt, or two-cell battery. 

23. The battery should be charged at a rate determined 
by its capacity in ampere-hours, the charging current, in 
amperes, being equal, for an ordinary battery, to the am- 
pere-hour capacity divided by 10. Thus, a 65-ampere-hoar 
l)atter>^ should be charged at 6.5 amperes or an 80-ampere- 
hour battery at 8 amperes. Another and perhaps better 
rule is to charge at a rate not exceeding one-eighth or one- 
sixth of the ampere-hour capacity, and maintain this rate by 
gradually cutting out resistance until the voltage reaches 
2.4 or 2.5 per cell, when the cells begin to gas; then cut 
down the chargin<f current to one-twentieth of the ampere- 
hour capacity until the cells again gas freely, indicating a 
full charge. 


If the battery is charged from an incandescent-light cir- 
cuit, there must be used in series with the battery a resist- 
ance sufficient to absorb the greater portion of the voltage 
of the charging circuit. For this purpose a bank of lamps 
is generally employed. As the internal resistance of the 
battery is so small as to be almost negligible, it follows that a 
100-volt lamp must be used for each 100 volts tension of the 
charging current, or a 110- volt lamp for a 110-volt current. 

24. Wiring connections for charging storage batteries 
from direct-current lighting and power circuits are shown 
diagrammatically in Fig. 11 (a), (b), (r), and (d). Connec- 
tions to a 110-volt lighting circuit are shown in Fig. 11 {a), 
A c3ouble-pole switch a, with fuses ^, is connected between 
the mains and the battery as shown. In series with the bat- 
tei-y r is a nvunber of lamps, by means of which the charg- 
^^fir current is limited to the proper amount. It is advisable 
^o c^onnect an ammeter d in circuit, though this is not abso- 
^^t:ely necessary. The number of lamps required depends 
^^^ the line voltage and on the charging rate of the cells. If 
^he line pressure is 100 to 120 volts and but three or four 
^^lls are to be charged with a current of 5 amperes, then 
^V"e 32-candlepower lamps requiring 1 ampere each, con- 
^^oted in multiple, as shown in Fig. 11 (a), will be suffi- 
^^^t If 16-candlepower lamps requiring \ ampere each are 
^s^d, it will be necessary to connect ten in parallel. With 
^ 5J20-volt circuit, there will be required twice as many 
*^ii3ps as with the 110-volt circuit, the second set of lamps 
^^& placed in series with the first. If the line pressure is 
SOO volts, it will be necessary to connect twenty-five 32-can- 
dlepower lamps in five rows of five lamps in series in each 
ro-^^ or fifty 16-candlepower lamps in ten rows, five lamps 
^ Genes in each row as shown in Fig. 1 1 (^). In case it is con- 
venient to charge at a lower rate, fewer rows of lamps will be 
^^^ed, but the time for charging will be proportionately 

86. Lamps form a convenient resistance, as they are 
^^jr obtained, but an adjustable rheostat is frequently used, 




as shown at r, Fig. 11 (c). The amount of resistance required 
in the rheostat can easily be obtained as follows: Let Nht 
the number of cells to be charged in series, then 2 -A^ will be 
the approximate voltage for charging, since each cell ihay 



itf / H H { 






Ftg. 11 


be taken as requiring 2 volts at the beginning ot the cha 
If ^ is the line electromotive force, then £" — 2 TV is the nt-'*^ 
ber of volts effective in forcing current through the cira't-' 
because the electromotive force of the cells is opposed to tt^ 


of the line. If / is the charging current, then the resistance 
of the circuit will be 

R = 


and this will be practically equal to the amount of resistance 
required in the rheostat, because the resistance of the cells 
is very low. 

Example. — Tweiity storage cells are to be charged from a 220-volt 
circuit; how much resistance should be connected in series with them, 
if the charging current is to be 5 amperes ? 

SoLin ION. —Here E = 220, N= 20, and / = 5; hence, applying the 

220 — 2 V 20 
jR = ^^ = 86 ohms. Ans. 


This resistance should be adjustable, so that some of it can ^ cut 
out as the voltage of the cells increases, and it must be made of wire 
large enough to carry at least 5 amperes without overheating. 

Charging with resistance in series is at best a makeshift, 
because it involves a large loss of energy; but in the case of 
small, portable batteries, this waste is not a very serious 
matter, especially as the use of the series resistance gives 
the most convenient and simple means of charging from 
existing circuits. 

36. Sometimes cells are charged from constant-current 
arc-light circuits, •but the practice is dangerous, and this 
source of charging current should never be used if any other 
is available. Constant-current arc-light dynamos generate a 
very high pressure, and, as arc- light lines are nearly always 
grounded to a greater or less extent, there isqtiite an element 
of danger in working around a battery that is being charged 
from such a source. Great care must be taken to see that 
the arc-light circuit is not opened when the battery is being 
switched on and off. This method of charging is shown in 
Fig. 11 {d), where /, / represent arc lamps. In this kind of 
circuit, the current is maintained at a constant value, usually 
from 6 to 10 amperes, so that when the battery is to be charged 


it must DC placed in series with the lamps. The battery is cut 
into circuit by means of a special switch, called a consumer s 
s^vitchy which is constructed so that it will neither open the 
circuit nor short-circuit the battery. This is done by means 
of a contact point c connected to a resistance r. 

When the switch blade is moved to the dotted position, 
the resistance is first placed in series so that the line is not 
opened, and at the same time there is no short-circuiting of 
the battery. It will be noticed that, when the switch is in 
the dotted position, the resistance is in parallel with the bat- 
tery, so that part of the main current is shunted around the 
battery. For example, the main current might be 9 amperes 
and the required charging current 5 amperes, in which case 
the resistance should be such that the difiEerence between the 
two, i. e., 4 amperes, will flow through it. The pressure 
between the terminals of the resistance is equal to the elec- 
tromotive force of the cells ; hence, if / is the current shunted 
through the resistance, E the voltage of the series of cells, and 
R the resistance, then R is easily obtained from the relation 

27. When charging a battery from any source, especially 
when there is any doubt as to the direction of flow of the cur- 
rent, a test should be made to determine whether or not the 
positive plates are connected to the positive pole, so that the 
current flows in at this pole when the battery is charging. 
A simple method of doing this is to attach two wires to the 
mains, connect some resistance in series to limit the current^ 
and dip the free ends into a glass of acidulated water, keep- 
ing the ends about 1 inch apart. The end from which 
bubbles of gas are given off most freely is connected to the 
negative main, so that the main to which the other end 
connects is the one to be attached to the positive pole of the 
battery. Another convenient method of testing the polarity 
is by means of a Weston voltmeter, or any instrument of 
similar type, which will give a deflection over the scale 


only when the voltmeter terminal marked + is connected to 
the positive line. 

The positive terminal of a storage battery is usually 
marked +, and is sometimes painted red. The positive 
terminals of the two cells commonly installed on automobiles 
and motor boats should be connected by separate wires to 
the two terminals of a double-throw switch located in an 
accessible position. 

28. If a voltmeter or hydrometer test of a single cell of 
the battery shows it to be out of order, it should receive 
individual attention until it is restored to proper condition. 
If the density of the solution is incorrect, it should be altered 
as already indicated. If the voltage of one cell is low when 
the rest are charged, cut it out and recharge it separately. 
If the cell still fails to come up to the proper voltage, it is 
likely to be due to the presence of active material that has 
detached itself from the plates and fallen to the bottom, where 
it may have bridged the space between two plates, thus short- 
circuiting the cell. The novice had better not attempt to med- 
dle with a battery in this condition, but with some electrical 
experience one may remove the pitch with which the top of 
the battery is sealed, and, taking off the hard-rubber cover 
beneath, lift out the battery plates and wash them in cle^n 

The battery jar also should be emptied, cleaned out, fresh 
aoid solution put in, and the plates put back in the acid as 
soon as possible. The battery may be sealed up again by 
naelting the pitch and pouring it over the cover, taking care 
iK>t to stop up the vent hole. If the battery terminals 
l>^^XMne dirty from acid creeping up on them, clean them 
^v^th ammonia and a tooth brush. Ammonia may also be 
^s«d to neutralize acid that may be spilled or that may get 
^*'*^ the clothes or fingers, but to be effective it must be 
^-Pplied immediately. 

29» When the battery is not to be used for some time, it 
**^y be laid up by one of the two following procedures, 


which are those recommended by the National Battery Com- 
pany for their cells, and are equall)c applicable to others. 

First Method. — When, for any reason, a battery is not to 
be used for some length of time, it may be kept in good con- 
dition by giving it an occasional freshening charge. This 
charge should be given at intervals not greater than 2 
months, and preferably once in every 6 weeks. The fresh- 
ening charge should be at the rate of one-twentieth of the 
ampere-hour capacity of the battery, and should be contin- 
ued until the battery gases freely. This is by far the sim- 
plest and the best way to tkke care of a battery when it is not 
in actual service, as it will always be ready for immediate 
service when needed. When a battery cared for in this man- 
ner is again placed in service, the additional precaution may 
be taken to give it the three-quarter discharge and the 
charge following, to insure the full capacity, as described in 
the second method. 

Second Method. — If a battery is not to be used for some 
time, and cannot receive an occasional charge to keep it in 
good condition, it should be put in dry storage. To put a bat- 
tery in dry storage, it should first be fully charged and given 
an overcharge ; then the electrolyte should be emptied out 
and the cells allowed to stand until the negative plates begin 
to steam, which will be within about half an hour. 

The next step is to cool the plates. Fill the cells with dis- 
tilled water, and allow them to stand for about 10 minutes; 
then pour out the water, and again allow them to stand 
until the negative plates steam quite freely. This operation 
should be repeated until the plates lose their heat. 

Next put in the acid solution that was removed, and allow 
the cells to stand for 1 hour, after which again remove the 
solution and put the battery away in a dry place where the 
temperature will not get below the freezing point. 

After the last process, in which the plates are allowed to 
soak in the acid solution for 1 hour, they should be watched 
for a day to see that they do not again become heated. Should 
it 1^ found that they are heating, the acid-soaking process 
should be repeated until there are no more signs of heat. 


While the plates are still drying, it is possible that night- 
fall may come on. The condition of the plates may still be 
such as to make it inadvisable to leave them. If inconve- 
nient or impossible to continue the above process during the 
night, fill the cells with acid and allow them to stand until 
morning, when the process may be continued. 

30, To put these cells again into commission, fill them 
with an acid solution having a specific gravity of 1.21, free 
from impurities, and charge at the minimum rate as stamped 
on the name plate until fully charged. This will require 
about 40 hours. During this time, the battery should be 
watched closely, and the temperature of the acid taken occa- 
sionally. If the temperature should get above 100° F., the 
charging current should be cut off for a few hours and the 
cells allowed to cool; then the charge should be continued at 
the minimum rate until the cells have been charged for 40 
hours. It would then be strongly advisable, in order to 
injure the full capacity of the plates, to give the cells about a 
three-quarter discharge; then charge them again as before 
until they gas freely, when the battery will be ready for 

The simplest way to secure a three-quarter discharge, 
where the battery is being charged through a lamp circuit, 
IS to reverse the connections of the battery, that is, connect 
the negative charging wire to the positive terminal of the 
battery and the positive charging wire to the negative ter- 
minal, and allow the battefy to discharge until the voltage 
has fallen to about one-quarter that at full charge. 

This discharge should'be conducted at a rate of one-tenth 
the capacity of the battery. If, for example, the capacity 
of the battery is 40 ampere-hours, this discharge should be 
carried on at a 4-ampere rate for a period of about 7 hours. 
The battery connections should then again be reversed, and 
a charge carried on at the minimum rate until the battery 
gfases freely. It is better not to make a practice of recharg- 
ing* storage batteries when they are less than half discharged. 




31. In their application to the marine engine, spark 
colls are broadly divided into two classes: the ordinary 
inductance coil using the primary current only, and the 
double-wound jump-spark induction or Ruhmkorff coil, in 
which a secondary current of high potential is induced and 
strengthened by means of a condenser, usually placed within 
the coil box, or a condenser is provided for each coil; some- 
times the circuit is so arranged that one condenser may b& 
used with several coils. 

Induction coils are of various shapes and types, and ordi- 
narily are from 6 to 10 inches in leng^, rarely longer, and 
their construction and operation are so well known as to 
need no extended description here, ^hey should be kept 
as dry as possible, even though they are usually protected 
from dampness by means of paraffin wax, shellac, or similar 

33, Coils used in high-tension or jump-spark ignition 
are of two general classes, one with a vibrator that opens 
and closes the secondary circuit and is actuated by the elec- 
tromagnetism of the iron core of the coil, and the other with 
no vibrator. The former gives a rapid succession of sparks, 
and is the type used for the most part in jump-spark igni- 
tion ; while the other, which is rarely met in marine prac- 
tice, gives a single large spark on breaking the circuit 
This latter type is used for the most part in motor-cycle 
work where minimum weight is essential. 

The object of primary ignition will be referred to latet in 
connection with magneto-generators, with which it is prin- 
cipally used. Where batteries are used, the jump-spark 
system is almost invariably employed. 

33. Fig. 12 shows the appearance of a typical jump- 
spark coil for one cylinder. It is a standard four-terminal 



, in whicli the binding posts a and h are, respectively, 
positive and negative of the secondary coil, and the 
ing posts c and d connect, respectively, to the engine 
! and the battery. Posts b and c may be connected 

together, since both are grounded. The fiat vibrator or 
trembler spring e is adjusted with respect to its tension 
by the screw_/i and g is the customary platinum-tipped con- 
tact screw against which the vibrator works. 

In Fig. 13 are shown the connections to a coil o£ this t?pe. 

The secondary, or spark-plug, terminals are shown at a and 
b, the current flowing from a to the insulated electrode of 
the plug, returning from the grounded electrode of the 
plug' to the groiuided terminal b, which may be connected 




to the negative terminal of the primary winding of the 
coil. Through the wire c^ current flows to the coil from 
the battery rf, when the switch e is closed and the insulated 
member of the timer/* is in contact with tjie grounded mem- 
ber of the timer, the direction of the current being indicated 
by the arrows. The switch may be placed either between 
the negative terminals of the battery and the timer, as 
shown, or between the primary terminals and the coiL 

34. In Fig. 14 are shown, diagrammatically, the connec- 
tions of the coil shown in Fig. 12, the switch this time being 
located between tHe batteries and the coiL Two batteries 

PlO. 14 

tf, a are shown, either of which may be used by taming the 
switch d. The passage of the current is through one or the 
other of the batteries a, a^ through the switch ^, primary 
winding r, vibrator rf, contact screw e^ insulated member of 
the timer/, and finally into the engine frame, as indicated 
by the ground ^^ from which it returns to the negative 


minal of the battery. The secondary winding is shown 

4. As the secondary current is induced on rupture of 
I primary, its direction is the same as that of the primary, 
ich makes terminal i the positive. The negative termi- 

j of the secondary winding is shown with an independ- 
: ground connection g^ but it might equally well be con- 
:ted to the primary winding, in which case the current 
uld return to it through the battery and switch. This 
•ticular coil has two condensers: the regular condenser ky 
ich is found on all jump-spark coils, and which absorbs 
extra or selfi-induced primary current at the moment of 
)ture ; and another condenser /, which comes into play in 
e the engine speed outruns the speed of the vibrator, and 
latter sticks — that is, refuses to work fast enough to 
p time with the engine. If this occurs, the only rupture 
hat taking place at the timer, and the extra current then 
s to the condenser / by way of the ground g on the 
ine frame, and the wires m and «, there being then no 
ik at the vibrator. 

5. The feature discussed in the last article is not found 
all coils, but it is useful with a high-speed engine, as 
it coil vibrators, on account of their inertia, do not work 
ibly at engine speeds exceeding 1,200 to 1,400 revolu- 
s per minute. Of course, the rupture at the timer 
irs somewhat later than at the vibrator, since the latter 
ars soon after the timer makes contact; and, therefore, 
he critical point when the vibrator begins to stick, the 
er will need to be advanced in order to get the same 
rk time. With a little practice, the operator learns to 
>gnize the point to which the timer must be advanced. 
is shown a safety spark gap^ as it is called, which is pro- 
ed inside the case of all spark coils to prevent overstrain- 
of the insulation, in case an abnormally severe current is 
t through the coil. This gap is provided with a pair of 
es soldered to the bottom ends of the binding posts a and 
?ig. 12, and is about ^ inch long, that being equal to the 
atest air gap that the spark is ordinarily required to 




jump. This is equivalent to about ^ inch under average 

36. Every spark coil requires occasional attention to 
the contact points of the trembler, as these become worn 
and pitted under the large currents often employed. Spe- 
cial means are commonly used to prevent the adjusting 
screws of the trembler from working loose. In the coil 
shown in Fig. 12, these means take the form of clamp screws 
//, by which the split yoke in which the contact screw g is 
threaded may be drawn tight on the screw. As the adjust- 
ment must be very accurate, and the vibration of the trem- 
bler quickly brings to light any looseness, some such provi- 
sion as this is very necessary. 

37. A special form of trembler, found on some French 
coils, is shown in Fig. 15. For comparison, Fig. 16 shows 



Fig. 15 Flo. 16 

the hammer trembler of the ordinary coil. It will be 
noticed that, in the latter, contact between the trembler 
spring a and the screw b is broken almost instantly when 
the hammer begins to move, the only delay, after the ham- 
mer is in motion, being that required to allow the current 
to build up in the coil, and to allow the hammer head to 
travel as far as the yield of the spring will allow before the 
rebound of the spring carries it toward the core c. As the 
hammer head is quite heavy, it is evident that there is a 


limit to the speed of the vibrator, due largely to the inertia 
of the head. The trembler shown in Fig. 15, on the other 
hand, consists of a pair of flat steel blades, which, while not 
so hard as to retain much permanent magnetism, are still 
hard enough to act efficiently as springs. The lower spring 
a is supported in the usual manner, and the upper spring b 
is riveted to it at the point c. Normally, the blades sepa- 
rate slightly, and the upper one makes contact with the 
screw d. Consequently, when the circuit is closed, the 
lower blade a is first attracted, and it moves downwards; 
while the upper one, by virtue of the initial spread between 
the blades, remains in contact with the screw. When, how- 
ever, this spread has been fully taken up, the upper blade is 
pulled out of contact by the continuing motion of a ; and, as 
« has by this time acquired a considerable velocity, the sepa- 
i^tion between b and d is very abrupt, thus causing an 
energetic excitation of current in the secondary coil. By 
reason of the extreme lightness of these springs, and 
^cause of the fact that contact is maintained for a consid- 
erable fraction of the working period of the trembler, the 
speed is exceedingly high, without sacrifice of efficiency, 
^d without preventing the magnetism from adequately 
"Elding up between breaks. 


38. The care of the spark coil is limited to seeing that 
the vibrators are kept clean and properly adjusted. The 
platinum points of the contact screw should be kept flat and 
clean, and to this end the contact screw should occasionally 
be taken out, and both contacts dressed with a fine file. If 
the adjustment of , the contact screw against the spring is too 
tight or too loose, the operation of the coil will be erratic, 

and in the former case the demand for current will be 


39. Most coil vibrators now made have two adjust- 
ments: one for spring tension, involving also the distance 


of the vibrator head, or armature, from the core, and one 
for the pressure of the contact points. As there are so 
many varieties of coil, an exact rule for their adjustment 
can hardly be laid down; but it may be said in g-eneral that 
the armature should be as close to the core of the coil as is 
consistent with clearance to insure that it cannot touch the 
latter. The sprin^^ should be stiflE enough to insure rapid 
vibration, but not so stiflE that a considerable current is 
required to attract the armature; and the contact screw 
should bear with a light pressure, to permit the use of a 
small current, but not so lightly as to make the vibrator slug- 
gish. The faster the vibrator works and the smaller the 
interval between sparks, the smaller will be the angle 
through which the engine crank will turn in that interval, 
and the more uniform will be the spark time from one cycle 
to the next. 

The best procedure in adjusting is, first, to run the contact 
screw back until it is out of contact; then, to adjust the 
spring until the armature is from ^ to /y inch from the core 
— the lighter and more rapid it is, the closer it can be 
adjusted — and, finally, to run down the contact screw until 
a clear and high, but not a tinny, note is produced when the 
circuit is closed. Then connect an ammeter in the priman' 
circuit, and note the reading when the engine is standing 
still and the vibrator working. It should read from .25 to .5 
ampere, for a moderate-compression motor; but, if the com- 
pression is high, from .5 to 1 ampere may be required. By 
adjusting the spring slightly, the current can be reduced 
without making the vibrator work slower. When the mini- 
mum current has been found, note whether the engine 
develops its full power when it is running. If not, try turn- 
ing the contact screw down a little more; but do not leave 
it down unless it improves the power, as it simply w^astes 

40. If the cnpfin** has more than one cylinder, tune the 
vibrators separately and as nearly alike as possible. When 
a coil is supplied with the engine, it is well to note its 


sound and adjustment when the engine is received from the 
factory, and to restore this sound as nearly as possible when 
the coil requires attention. 

A weak battery will need a vibrator adjustment different 
from that for a fresh battery, the contact screw bearing 
with a lighter pressure and the vibrator speed being neces- 
sarily somewhat slower. 

Occasionally, it will happen that the insulation of the sec- 
ondary winding on the coil will break down, which will 
cause the coil to give a weak spark or none at all, even if 
the battery is fresh and the vibrator adjustment good. 
Sometimes, also, the wires leading to the condenser break. 
This results in excessive sparking at the vibrator and 



4t\. The chief difficulty experienced in connection with 
the jump-spark system of ignition is found in maintaining 
proper insulation of the secondary circuit. On account of 
the carbon gradually deposited over the interior of the com- 
bustion chamber from the fuel and the slowly-burning cyl- 
inder oil, it follows that the most difficult place in the 
secondary circuit to keep properly insulated is the point 
where the spark is produced. The problem of insulation 
here Jias been solved by the use of the spark plugr, a sec- 
tion of a representative type of which is shown in Fig. 17 (of). 
A spark plug consists of a steel shell a that screws into a 
threaded hole in the wall of the combustion chamber; a por- 
celain or mica insulator by and a threaded bushing r, by the 
aid of which, with suitable packings d^ the porcelain is 
made air-tight in the shell ; and a metal stem r, made air- 
tight by packing or cement, according to its form. The 
seconda\y current is conveyed from the positive terminal of 
rhe coil to the binding post /", at the end of the stem e by an 


insulated cable, and the spark jumps from ^ to a projecting 
point g connected to the shell a. From the shell, the sec- 
ondary current goes through the engine frame back to the 
negative terminal of the secondary winding, which, like the 
battery, is groimded on the engine. By detaching the cable 
from fy the plug may quickly be unscrewed for inspection 
and cleaning of the porcelain. 

The construction of the plugs shown in Fig. 17 (^), (r), 
{//), (r), and (/) is but little different from that shown 
in (tf). What is known as a closed-end plug is shown in (^), 
the points a and b being located in the nearly closed end of 
the plug. The point a is concentric with the plug-end 
opening into which the point b projects from one side. 
The so-called open type of the same plug is shown in (r), 
the point a projecting beyond the end of the plug, as shown. 
The point b can be turned away from a to increase the gap 
between the points. In the plug (</) the point a is mounted 
in the hexagonal head b of the insulated bolt c for conduct- 
ing the current and for keeping the plug tight, the spark 
bridging the gap between the point a and the threaded 
shank.of the plug. In the plug (r), the insulated electrode a 
resembles a star. The spark occurs between the projections 
of the insulated electrode a and the threads of the grounded 
electrode b. In the plug (/), the insulated electrode is 
threaded and the opening b of the grounded electrode is star 
shaped. In the plug (^), the insulated electrode a is 
wrapped with sheet mica ^, and then surrounded with mica 
washers c pressed closely together under heavy pressure and 
held in place by a brass nut d and washer. The groimded 
electrode e is fastened in the bushing /. Spark plugs are 
sometimes protected against the short-circuiting effect of 
moisture by means of a porcelain hood or cap a. Fig. 17 
(A), having a recessed neck b on one side to receive the 
wire r, which is connected to the plug by a terminal link d 
in the manner shown. 

43. While there are a great variety of spark plugs on the 
market, each with some special features of advant^e that 

M»— 7 


may or may not be possessed by others, the chief require- 
ments of a good spark plug are the following: 

1. The insulating material of porcelain or mica between 
the central electrode or stem, which is connected to the pos- 
itive terminal of the coil, must not be too easily coated with 
carbon deposit, where exposed to burning gas and oil 
vapors. It is to be remembered that the electrical resist- 
ance of any gas increases considerably ^ the gas is com- 
pressed, so that, although the current may jump between 
the proper spark points when the plug is in the open air, it 
may find the resistance between these points too great when 
the plug is in the cylinder and the charge is compressed, 
and will take an easier path through the carbon coating on 
the porcelain. Practically the same thing will invariably 
happen if the porcelain is cracked, for the same reason, 
namely, that the current will take the direct route through 
the crack rather than the difficult route from spark point to 
spark point through the compressed gas. The leakage 
through the carbon deposit is made as difficult as possible 
by giving the leaking current a considerable distance to 
travel, and there are also special devices sometimes 
employed to prevent the collection of carbon. 

2. The plug must be easily cleaned of whatever carbon 
maybe deposited on it. To clean the plug properly, it must 
be taken apart, and it must not be too difficult to reas- 
semble the parts and make the plug gas-tight, nor must the 
packing process endanger the porcelain more than 

3. The plug must fit the standard sizes of threaded 
spark-plug holes, and must not be unduly expensive t 
replace. Among the sizes most used is the so-called metri 
size, the proportions of which are based on the metric sys 
tern of measurement. Most of the imported spark plugs 
are of this size, which is approximately the size of a -J-inc 
pipe tap, but is not tapered. American spark plug^ ar 
either of the ?r-inch or tlie f-ineh pipe sizes. The pi 
sizes are tapered, and depend for ti^ditness on the plu 
being screwed in ti.t;lilly. This method is not altogethe 


satisfactory, as the thread in the engine wears and permits 
leakage, which causes the plug to heat; and both the engine 
and plug tapers are liable to variations that may make one 
plug screw well into its hole while another catches only a few 
threads, and consequently is not so well placed for prompt 
communication of flame to the compressed charge. Plugs 
that are not provided with tapered threads are made gas- 
tight by gaskets of asbestos covered with thin copper 

43. It is desirable, though not essential, that the spark 
points should be of platinum, since when made of this metal 
they do not bum away to any appreciable extent. When 
not made of platinum, they are often made of a special alloy 
of steel and nickel, which resists oxidation nearly as well as 
platinum. The air gap between the spark-plug points should 
not exceed -^ inch, nor be less than -^j inch ; the best size is 
about midway between these dimensions. In case a battery 
gives out and there is no other at hand, the car may be kept 
going for a short distance by pinching the spark-plug points 
a little closer together, to reduce the resistance offered by 
the gap. 


44. A plug whose porcelain is slightly covered with soot 
can be kept in action by the use of an auxiliary spark-g^ap 
device, two forms of which are shown in Fig. 18 {a) and (d). 
This device consists simply of two insulated terminals a and d 
with points separated by an adjustable gap, usually about one- 
sixteenth inch in length. In the form shown in Fig. 18 (a). 
the terminals are enclosed in a glass tube c to prevent possi- 
ble ignition of stray gasoline vapor. This form is connected 
in the secondary circuit by means of the connecting screws 
d and t. The form shown in Fig. 1 8 (d) is attached to the 
binding post of the spark plug itself, and the spark jumps 
from the point a to the binding post d. The base /is made 
of fiber. 

When the primary circuit is broken by the timer, it 


requires a short time for the induced current in the second- 
ary circuit to build up to its full voltage; and, in order that 
the full voltage may be reached, it is necessary that the first 
small quantity of energy induced in the secondary shall not 
be allowed to escape. If the spark-plug insulation is not 
perfect, or if the plug is sooted, the charge first induced 
leaks away either through the insulation or over the soot 
deposit, and the voltage does not become great enough to 
force the current across the gap and produce a spark. By 
the use of an auxiliary spark gap outside the cylinder, the 

Pig. 18 

secondary circuit is held open, this leakage is prevented, and 
the induced current builds up to its proper voltage, so that, 
when the gap is finally bridged, the entire energy of the 
induced charge is employed in producing the spark. With 
the recent improvements in plugs, and by proper attention 
lo the carbureter adjustment and to lubrication, sooting of 
plugs is avoided to a greater extent than it used to be, but 
there are many occasions when the auxiliary spark gap is 
exceedingly useful. 




45. Timers^ or primary commutators, as they are 

commonly called, are devices whose object it is to close the 

igrnition circuit at some prearranged point or points in the 

TCATolution of the crank-shaft, keeping it closed sufficiently 

long to insure ignition, and then opening it, no matter 

whether the engine is of the single or the multi-cylinder 

typ>e. The principle of operation of all timers is practically 

th.o same, but the length of the time of contact varies, and 

in. some cases an extremely short life of the battery is the 

result. Some timers, especially those on cheap two-stroke 

niarine engines, are arranged on the engine crank-shaft, 

miprotected by a cover, with nothing whatever to prevent 

^^y gasoline vapor in the lower part of the boat from taking 

fif^, as there is always a spark or small arc at the time of 

breaking the contact. 

46. It might be supposed that a multi-Cylinder engine 

would be regularly equipped with a single spark coil, whose 

primary circuit would be closed as many times in each cycle 

of the engine as there were cylinders to be sparked, and 

wliose secondary current would be led by a commutating 

device to the cylinder desired. This is, in fact, done in some 

Tecent cases; but the difficulty found until lately in confining 

^e high-tension secondary has led the majority of builders 

to prefer commutating the primary, and using a separate 

spark coil for each cylinder. 

47. In Fig. 19 is shown one form of timer, partly in 
section, and Fig. 20 shows it wired for connection to the 
^^gine. The case consists of a large fiber disk a, with a thick 
raised rim ^, in which are embedded four brass contact pieces r, 
^ch connected to its proper coil. The shaft runs through 
^e disk a, which has a bearing on the shaft, and carries a 


hub d and pivoted lever e, on one end of which is a roller / 
that runs against the internal rin^ b and makes contact with 
the insulated segments c. A spring g connected to the 
other end insures good contact. A rod ctmnecting the arm k 
with a lever provided for the purpose of advancing' the sparV 
and called the spark advance lever, holds the disk a from 
rotaMng with the shaft and determines its position. This 

sort of timer is arranged to be oiled freely, and the oil does 
not interterc with its working. The arrangement shown in 
Fig. 20 includes a button a on the steering wheel of an auto- 
nmbile. by which the currentmaybetemporarilyintermpted 
at the will of the operator. This is sometimes convenient 
when coasting, or in managing the machine when surrounded 
by other vehicles. Two pair of storage cellsin their cases are 
represented by * and c. Current from the storage batteries 
pjissfs to the prim;ir\- windings of the coils in the coil box d, 
iIk- tiirri.-iit inihiccd in the SL'Condary windings of^the coils 
passing lu fat-h of the spark plugs in turn when the proper 
L-ontact at the linicr is made. 

48, Because of the arrangement of the cranks, and in 
order tn take advanta:.,^e of the alternate movements of the 
pistons, iIk- onltT <ir cxploslotts in the several cylinders 

; 18 


must be either 1-2-4-3 or 1-3—1-2, these numbers correspond- 
ing- to the numbering of the cylinders as shown in Fig. 30, 
where the order of firing is 1-3— i-3. If the purchaser of an 
automobile or motor boat is not sure as to the order of firing of 
his engine, he can easily determine what it is by turning the 

engine slowly and watching the order in which the exhaust 
"Iv-es open, which will indicate the order in which the 
charges in the cylinders must be ignited. 

^9, That the order of firing must be as just indicated 
will be apparent by referring to Fig. 21, which is a diagram- 
niatic illustration of a vertical four-cylinder four-cycle engine 
sbo\jving the relative positions of the pistons. The arrange- 
'"&nt of the crank-shaft is such that, while the pistons in cyl- 
inders 1 and 1 are descending on their working and suction 
proles, respectively, the pistons in cylinders 2 and 3 are 
"loving upwards on their compression and exhaust strokes. 
™ptesenting the working, fxhaust, suction, and compression 


strokes necessary to complete a cycle by the letters IV, £, S, 
and C, the following diagrams. Fig, 22 (a) and (it) serve to illus- 
tratehow the movement of the exhaust valves makes it possible 
to determine the order of firing, which is dependent on the 
operative relations between cylinders 3 and 3; that is to say, 
whether the compression orthe exhaust stroke is to take place 
in cylinder No. 2 or in 
cylinder No. 3 when 
the order of events in 
cylinders No. 1 and 
No. i are as indicated. 
At the top of the dia- 
grams, Fig. 22 (a) and 
{d) the aumbers of the 
cylinders correspond- 
ing to flie numbering 
io Fig. , 31 are given, 
the arrows just below 
the numbers indicating 
the initial direction of 
movement of the pistons; while the figures at the left indi- 
cate the number of degrees of travel of the cranks necessary 
to carry the pistons to the beginning of the strokes repre- 

0= W C E S 

G° W E C S 

180° E \V S C iRO' E S W C 

3flu^ .-^ y; C W 3,;()° s C E W 

U\)' C S W E .540" C W S E 

',-i^f W C E S 720= w E C S 

si'iitiii liv tilt- luttcrs ]]\ E, S, and C, the beginning of the 
working strnkf. or poiiu ;ii which the charge is fired in 
cyliuder jVo. 1, lK.-in;f t;ikL-ii as zero. 


50. To complete a cycle in any one cylinder, the crank 
must travel 720°, or two revolutions; but, since there are 
four cylinders, the crank-shaft receives four power impulses 
during two revolutions, and hence, in order that the appli- 
cation of power may be uniform, the impulses must occur 
180® apart. Fig. 22 {a) shows that, when the working stroke 
in cylinder No. 2 begins at 180°, it will be necessary to fire the 
charge in cylinder No. 4 at 360°, following with cylinder 
No. 3 at 640°, the cycle being completed just at the point 
where an explosion is about to take place in cylinder No. 1 at 
720**, or two complete revolutions. With this arrangement, 
the order of firing is shown to be 1-2-4-3. Fig. 22 (^), how- 
ever, shows that, when the second power impulse takes 
place at 180° in cylinder No. 3, the order of firing must be 

Si, Timers should be oiled and cleaned regularly, but 
^yond this they require little attention. Like any other 
part subject to friction and sparking, the timer will gradu- 
^ly Vear out and will require such attention and repair as 
Its Condition and construction may make necessary. 


It was once thought impossible to insulate the sec- 
ondary circuits of a jump-spark system so thoroughly that a 
^^n&le coil could be used to advantage for a multiple cylinder 
^^^ne, in connection with a secondary commutator or 
distributor, to deliver current to more than one sparkplug, 
^tely, however, this has been accomplished successfully, 
^e method being illustrated in Fig. 23, which is a diagram- 
matic view showing the arrangement of the wiring for a four- 
^y^inder engine. From the battery a, the current passes 
through the switch ^and the primary winding of the induc- 
tion or spark coil r to a binding post d connected with the 
iiisulated contact member of the timer e. On the cam-shaft, 
or any other convenient shaft that turns at one-half the 
speed of the engine, is a f our-lobed cam / that makes contact 



with the insulated member four times in each revo; 
the primary current being completed through the unins 
cam /, engine, frame, and ground connection at g. 

The spark coil generally has the usual vibrator, but 
times the single spark produced by breaking the cin 
the timer is considered sufficient. The induced cur 
led from the positive terminal h of the secondary coi] 



Fig. a 

heavily insulated cable /, to an insulated revolving 
whose end piisses over four insulated segments or 
heads/', k^ connected to the spark plugs as showTi. 
army may or may not actually touch the points k^ k^ 
it dcx?s not, the spark will readily jump the gap if the 
is small. The whole is suitablv encased to e: 
moisture. The impi^rtant |X»int in a successful distrib 
to have ver\- vr^xxi insulation. Hard rubber is the insu 
material common Iv used, and all electricallv active 
j>arts arc placed as ♦ar aiw:*: :.s nossible. 

g 18 



53. Commonly, the distributor is mounted on the same 
shaft as the timer. Fig, 24 shows this arrangement in sec- 
lion and elevation. The primary contact is made by a steel 
"ball a, held in place by a spring as shown. The sleeve b and 
contact cam c are carried on a shaft turning at one-half the 
speed of the engine. The secondary current is led to the 
binding post (/, through which 
it travels by way of the con- 
tact ball e to the brass strip/ 
that runs over the hard-rub- 
ber surface g, and makesi 
contact with the flat-headed 
screws h, h embedded therein. 
These screws carry the cui- 
rent to the several spark 
plugs. Efficient insulation 
between the primary and the 
secondary is secured by the 
long, hard-rubber stem ( on 
which /is carried. The cas- 
ing/* is rotated for advance 
or retardation of the spark 
by the arm k. It is evident 
that the movement of this 
arm advances or retards both 
primary and secondary con- 
tacts aUkc. A ball bearing / 
is shown, which is sufficient 
to support /, as the latter 
carries little weight. 

54. Ill the combined timer and distributor shown in 
Fig. 25, the .shaft a carries at its extreme end the timer 
cam b, which has as many lobes as there are spark plugs t« 
be supplied. These lobes successively make contact with 
the steel plunger e. This plunger is supported in a hard- 
rtibber casing rf, and by meansof asleeveisfastened on fl for 
rotation according to the spark advance recjuiix^d. Attached 



to fz by a taper pin is a hard-rubber barrel c, carrying a 
tact ring/ extending clear around it and connected thn 
a longitudinal strip with a single contact segment neai 
left-band end of e. The secondary current is carried tc 
ring/by the contact plunger^, and four other phit 
mounted in d make contact successi^-cly with the aegi 
connected wtth/i The hard-rubber moantin^ affoids 
cient insulation. To the right-hand end of </ is scr^w 

metal ring li, from which projects an arm for rotatH 
advance or retard the spark. The light casting i alFoi 
bearing for the shaft and for /;, and can be screwed to 
convenient support, the shaft a being ojjerated by a chfli 
flexible shaft driven from the cam-shaft. A glass fro 
tlirough which the action of the timingcam maybe watc 
is provided. 




66. Owing to the fact that the ignition circuit of a four- 
cylinder engine is closed twice in each revolution, there is a 
gfreat consumption of battery power; and, in order to escape 
the annoyances of frequent recharging of storage batteries 
or replacement of primary cells, various forms of mechan- 
ically operated current generators are often employed. The 
simplest of these in some respects is a miniature dynamo, 
taking the place of a battery, with little or no change in the 
coils and wiring. It is generally used in conjunction with 
jump-spark coils, but if employed with primary-spark 
apparatus no coil is required, as the self-induction of the 
armature furnishes the extra current for ignition. Dyna- 
mos for this purpose are commonly of the iron-clad type to 
exclude water and protect the field windings, and the arma- 
tures have a number of coils so that the generators give a 
practically constant current. 

66. Generators used for ignition are sometimes 
employed for furnishing light and for charging storage bat- 
teries, the ignition system being so arranged that the excess 
current generated when igniting the charges in the engine 
is used in charging the storage batteries, which in turn sup- 
ply current for starting the engine or furnish current for a 
limited number of small incandescent lights. 

The difference between a dynamo and a magneto is that 
the dynamo consists of an armature rotated through a field 
composed of electromagnets, while in the magneto the field 
is a permanent magnet. The magneto can be run in either 
direction, while the dynamo as usually constructed for the 
purpose can be run in one only, as to run in both directions 
would necessitate double sets of brushes. 

Low-tension magnetos are used for marine gas-engine 
ignition, but only with the make-and-break system, because 


magnetos, as usually constructed, generate alternating cur- 
rent, and the inductance coils commonly employed with the 
primary ignition system can be operated only by means of 
direct current from a dynamo. 

57. Dynamo-electric ignition generators require very 
little attention beyond occasional oiling, polishing of the 
commutator with a piece of fine sandpaper, and trimming 
the brushes. They are, however, rather bulky and quite 
heavy, and their efficiency per pound is much below that of 
special types of magneto-generators. When the motor is 
turned by hand, the speed of the dynamo is commonly too 
slow to generate a good spark, and it is necessary to use a 
dry or storage battery for starting, and to switch to the 
dynamo afterwards. If, as is usually the case, the dynamo 
generates a more powerful current than the batter}^ gives, 
this arrangement has the slight drawback that the coil 
vibrators do not generally work equally well with both cur- 
rents, and frequent adjustment is required. 

58. It is quite feasible to use the dynamo simply to 
charge a storage battery, the current for the coils being 
taken from the latter, the speed of the dynamo being just 
high enough to make sure that the battery will not dis- 
charge through the dynamo against the voltage of the iat- 
ter. The positive terminal of the dynamo is then connected 
through an automatic switch with the positive of the bat- 
tery, and the negatives of the dynamo and battery are con- 
nected direet. The rest of Uie ignition circuit is the same 
as usual. The switch, which is worked automatically by an 
electromagnet in the dynamo circuit, breaks the charging 
connection when, through the slowing down or stopping of 
the motor, the dynamo speed drops too low to generate the 
required voltage for charging. The most suitable dynamo 
speed will then be such as to give a voltage on open circuit 
of T or S volts for charging a two-cell batiery, and 9 to 10 
volts 1'<»r a tliree-eL-11 battery. 

51), All iL^nition dynamos have self-exciting field mag- 
nets, and from thi^ fat't they liave a tendency to oversensi- 


tiveness, by which is meant that the current they give is 
more dependent than it should be on the speed of the 
machine. The reason for this is clear when it is remem- 
bered that an increase in speed of the armature not only 
increases the voltage of the armature current, but, as part 
of this current is used to excite the field magnets, intensifies 
the magnetic field also, producing a still further increase in 
the intensity of the induced current in the armature. This 
is one of the principal reasons for employing a centrifugal 
g-Qvemor, by which the speed of the dynamo is prevented 
from becoming excessive. Of course, another reason for 
the use of a governor is to avoid unnecessary mechanical 
wear and tear, which would be considerable with working 
speeds in excess of from 1,200 to 1,500 revolutions per min- 
ute. Another device that partly remedies the oversensitive- 
ness just mentioned is to oversaturate the field coils; or, in 
other words, to wind them so that the soft-iron core will be 
fully magnetized at a comparatively low armature speed. 
From that point, as the armature speed increases, the 
increase in intensity of the fields is comparatively small, but 
of course the armature voltage is still free to increase in 
proportion to the armature speed. 

60. An objection to the direct use of the dynamo as a 
source of ignition current is that it is liable to give an exces- 
sively hot spark that quite rapidly burns away the contact 
points of the. tremblers on the coil, and may even endanger 
the insulation of the coils themselves. Moreover, the con- 
siderable number of coils of fine wire on the armature nec- 
essarily involves greater danger of an electrical breakdown 
than a smaller number of coils of coarse wire would. 


Ol. For the foregoing and other reasons, preference is 
frequently given to certain forms of magneto-generators 
having" permanent field magnets whose intensity is unaf- 
fected by the speed of the machine, and which have armatures 


of the simple H type with but a single coil of compara- 
tively coarse wire. These magnetos can be made very 
light, and the fact that the current induced in the armature 
fluctuates from zero to a maximum twice in each revolution 
is not a disadvantage, because the armature is always run in 
step, or synchronism, with the engine, and the circuit is 
broken for the spark when the armature current has its 
maximum value. Running in step, or synchronism, means 
that the rotations of the armature shaft and of tKe engine 
shaft are so timed that the maximum voltage of the current 
occurs at the point of the rotation of the engine shaft where 
the explosion should occur. By reason of the fact that the 
field magnetism is definitely limited and the armature can 
turn no faster than the engine, a magneto may be directly 
short-circuited on itself without injury, and this fact alone 
is of great value in protecting these machines from acci- 
dental electrical injury. Magnetos, like dynamos, are used 
for both primary and secondary-current ignition. 

62. In all continuous-current machines, the current, as 
it comes from the armature coils, is commutated at the 
brushes so that a direct current is delivered to the circuit 
In an ignition magneto, however, the direction of the cur- 
rent is of no consequence, and of the two terminals of the 
coil one is simply grounded on the armature core, while 
the other is led to an insulated collector ring on the shaft, 
from which it is taken off by a single brush. This results, 
on each alternate reversal of the current, in the grounded 
terminal being positive, instead of negative as conventional 
practice requires, and to guard against short circuits very 
careful insulation is required. 

G3, When an H armature is run in step,or synchronism, 
with the crank-shaft of a four-cylinder engine, it is only 
necessary to interrupt the annature circuit twice in each 
revolution at or near the points in the revolution where the 
current is the greatest. To insure the current being a maxi- 
mum at the moment of ignition, the armature shaft maybe 


rotated with reference to the engine shaft when the ignition 
time is changed, this being done by the use of a sleeve with 
an external spiral groove and an internal straight feather, 
which is interposed between the armature shaft and its 
pinion. By shifting this sleeve lengthwise, the armature is 
rotated through a limited angle in relation to the engine 

€4. If the induced current is sufficient, it may be unnec- 
essary to break the circuit exactly at the point where the 
current is greatest, and the sliding sleeve may be dispensed 
with. In this case, it is customary to break the circuit with 
thie current near its maximum when the engine is running 
at its highest speed, in order to give the most rapid inflam- 
iriation when it is most needed, and to permit the break to 
take place with a lower current when the speed is not so 
M^h. Owing to the intensity of the magneto-current, it is 
fot-ind that very little advance is required, compared with 
w'hat is necessary with a battery current. 

C5. liO'w-Tension Magrnetos. — So far, the description 
^^ the magneto applies to both the low and the high-tension 
typ^es. The low-tension magneto is operated in connection 
^'ith a make-and-break primary spark device. When used 
^^ automobiles, it is somewhat lighter in construction than 

on. stationary engines, owing to the higher speed at which 

automobile engines run. 

66. A diagrammatic illustration of the armature core 
^d pole pieces of a special type of low-tension magneto 
ctnployed in connection with make-and-break devices is 
shown in Pig. 26. In this magneto, the armature a is sta- 
tionary in the position shown, and it is enough smaller than 
the pole pieces ^, b to permit a soft-iron screen c to pass 
^tween them. The effect of this screen is to divert the 
lines of force at each eighth of a revolution, sending them 
alternately through the body of the armature core and 
through the ends, as shown by the dotted arrows. Since 
this reverses the current four times in each revolution, 



instead of twice, as is the case with the ordinary rotating 
armature, it will be evident that the induced voltage is 
much higher, mak- 
ing it possible to 
build this magneto 
so as to be very light 
in proportion to its 

67. Anotherlow- 
tension magneto is 
shown in cross-sec- 
tion and longitudinal 
section in Fig, 3T. 
It is driven by gea*^- 
ing at the speed oi 
'^'°- " the engine, the gea.-rs 

being set so that the range of the spark timer coincides witli 
tile effective range of the magneto-current. The armatu *^ 
pt>sitions determining the latter are marked on the magnet*'' 
iiiiii it is unnecessary' to change the angular relation of tftr3< 





v.jnnc when the spark isadvanced 
-.0 i->r!:'.C!i\i; fcii-^rt-s of coostruction are as 



The permanent mag^oets a have cast-iron pole pieces b 
fastened to them by screws. The cast-iron armature core c 
is wound with double silk-covered magneto-wire, and the 
ends of the core are screwed to hard brass disks d, into 
which the two shaft sections c, e are screwed and riveted. 
The object of this construction is to make a neater and more 
II compact winding of the armature than would be possible if 
ll the shaft passed right through the core. One of the ter- 

I minals is insulated, while the other is grounded on the 

II frame of the generator. The insulated terminal of the coil 
is connected to a hardened-steel boIt_/i insulated by a mica 

II bushing jf through the armature shaft, and the current is 

taken off by a hardened- steel contact pin h in the brass 

|l mounting /. carried by the hard rubber tube j screwed over 

ll the end of the bearing. From t, a flexible connector leads 

I to the binding post k. The entire magneto is provided with 

IIbii aluminum housing comprising a sheet cover /, and cast end 

|l plates m and «, together with top and bottom yokes o and/, 

ij and a cap ^ to exclude dust. The shaft is oiled by oilers r, r. 

\ The magneto is used without a spark coil, the binding post k 

being connected to the insulated electrode of a make-and- 

break igniter. The extra current required to give a large 

spark is supplied by the self-induction of the armature. 

68. HlKh-Tension Magnetos. — High-tension magnetos 
maybe divided into two general classes: those that simply 
talte the place of the battery and timer and deliver current 
to an induction coil of the ordinary construction, in which 
tile secondary current is induced; and those that comprise 
"> their construction all the elements of generator, timer, 
lid induction coil. One of the former type is shown in dif- 
ferent views in Figs. 38 and 39. The generator portion of 


magneto is substantially the same as that of the low- 

IfDsion magneto shown in Fig. 27. The current is collected 
from the insulated bolt a in the armature shaft by means of 
a small bronze bearing b, provided with an oiler, and bear- 
'ig against a stationary pin to prevent it from rotating, 
. Jlie other end of the armature shaft carries the timer or 


interrupter, which has a two-lobed steel cam c that works 
against a rocking arm d pivoted at its center. Contact is 
made between the screw e and a spring carried by the rock- 
ing arm d, and when the latter is tripped by the cam the 
upper end of the arm strikes the spring a blow that effects a 
quick separation of the contact points. The current is 
taken from the collector b to the spark coil and from the 
spark coil it passes through the rubber bushing /to the insu- 
lated contact screw e, and then through the frame of the 
magneto to the grounded terminal of the armature winding. 
The spark time is changed by rocking the housing g of the 
timer on its axis. This at the same time changes the point 
of maximum current in the armatiu-e winding in the follow- 
ing manner: 

The armature is surrounded by two soft-iron sectors A, //, 
Fig. 28, forming magnetic bridges somewhat similar to the 
screen of the magneto shown in Fig. 20. These are car- 
ried on brass end plates /, /, Fig. 29, secured to hubs that 
furnish bearings for the armature shafts. These hubs are 
supported in the end plates of the aluminum housing, and 
one of them has the timer housing fastened to it at its 
outer end. Consequently, the sectors k, h are rocked with 
the timer, and in this manner the direction of the magnetic 
lines through the armature is changed. The effect is the 
same as if the pole pieces themselves were rocked to change 
the point of maximum induction. 

69. The armature runs at the same speed as the engine, 
and delivers two sparks per revolution, one for each cylinder 
in turn. The spark coil is not provided with a trembler, 
only a single spark being produced at each rupture of the 
circuit by the timer. The positive terminal of the second- 
ary winding of the coil is carried by an insulated cable, 
through the top of the hard-rubber housing at the left end 
of the magneto, to a binding post connected to the flat 
springy. From this spring the current goes to the revolv- 
ing distributor arm k^ and is taken off by four insulated 
contact pins connected to the several spark plugs. The 


hard-rubber rod / carrying k is supported and rotated by the 
shaft ffty which is driven by the gear n and pinion o at one- 
half the speed of the armature shaft. The oilers p keep the 
shaft lubricated, and the centrifugal oil flange q prevents 
any surplus oil from reaching the hard rubber, 

70. The high-tension magneto just described, although 
very simple, does not attain the highest efl&ciency possible 
in apparatus of this type. It is apparent that in this class 
of magneto the extra current self -induced in the armature 
winding or the primary coil, which is utilized to give the 
spark in the primary ignition system, is objectionable 
because it prevents the instantaneous cessation of magnet- 
ism essential to the inducing of an energetic current in the 
secondary winding, exactly as when a battery is employed 
with a jump-spark coil. This momentary extra current is 
therefore absorbed by a condenser, and got rid of as far as 
possible. So far as it cannot be got rid of, it manifests 
itself by burning the contact points of the trembler and the 
timer, necessitating occasional cleaning or renewal. 

71, In Fig. 30, suppose that a is the armature wnnding; 
b^ the timing cam (arranged in this case for a single-cylinder 

Fig. 80 

engine) ; and c, the contact maker, the lever d being* sup- 
posed to be pivoted at its center, as in the timer shown in 
Fig. 29. The circuit is completed from the timer to the 
negative terminal of the armature coil through the engine 
frame, represented by the dotted line e. Suppose an induc- 
tion coil of the familiar sort to have a primary winding /, 
and grounded return connection g^ whose switch h is nor- 
mally closed. The secondary circuit is not shown. Fur- 
thermore, suppose that the primary winding is of moderately 


high resistance, and that the contacts of the timer are nor- 
mally closed, thus short-circuiting the armature on itself 
except at the moment of rupture, when it is desired to pro- 
duce a spark. As was just explained, a magneto can be 
short-circuited without injury; but the current in the arma- 
ture and coil will be high. If, now, the contact at c is 
broken when the current is at its maximum intensity, the 
result is not a complete breaking of the return path for the 
current, since the path through f-g-h is still open. Never- 
theless, the resistance of this path is considerably greater 
than the direct path through c-d-e. Considerable extra 
current will be induced and will necessarily travel through /. 
By this arrangement, it is seen that the momentary extra 
current, which is much more energetic than the regular 
current generated by «, even when the latter is short-cir- 
cuited, owing to the large current generated by the mag- 
neto on short circuit, is usefully applied to induce the 
secondary current in the spark coil. 

72. The location of the switch h shown in Fig. 30, 
although somewhat common, is incorrect, since if it is left 
open it entirely deprives the armature of a path for the 
extra current, and produces excessive sparking at the 
contact points r, where there ought to be no sparking at all. 
This is correfcted by arranging the circuit as shown in 
Figf. 31, in which the switch is so located as to short-circuit 

Pio. 8t 

the coil /"when closed. With this arrangement, the switch 
is opened when it is desired to use the toil, and is closed to 
stop the current, which is the reverse of the usual arrange- 
ment. Its effect is simply to let a run short-circuited as 
long as the switch is closed. 



73, Another ma^eto, the arrangement of which is 
shown in diagrammatic form in Fig. 3%, does not depepd on the 
momentary extra current, and differs from others in that no 
induction coil is used, the armature core itself serving the 

purpose of a coil. The heavy line a indicates the primary 
winding on the armature core. Rupture is produced by a 
timing cam 6, while a condenser c absorbs the extra current 
on rupture. The armature, however, is provided with a 
secondary winding d, in which the current for the spark 
plug e is induced. This system has the advantage of 

74, A very ingenious high-tension magneto, sectional 
and end views of which are shown in Fig. 33, depends 

neither on simple Rupture of the primary nor on directly 

utilizing the momentary extra current. Instead, the pr« 
marj' current is used simply to charge a condenser, and th< 
spark is induced in the secondary winding by the dJschaig* 




of this condenser through the primary winding of an induc- 
tion coil. Thus, the contact make-and -break by which the 
condenser is charged does not need to have its timing 
ctianged, the only change in time being that connected with 
ih^ condenser discharge. The coil is equipped with a 
vibrator, but the vibrator itself is employed only in start- 
ing, for which a battery is used, and is inoperative when the 
cuirent is supplied by the magneto. 

"75. The armature is of the H type with laminated core 
<z, and runs in ball bearings. On the armature shaft is 
nnounted the regular 
primary interrupter b, 
having a circular cam 
with two lobes, thus 
inaking and breaking 
the circuit once for each 
stroke of the engine, 
which is here supposed 
to have four cylinders. 
" second shaft c is run ; 
''? the pinion and gear 
^ and / at one-half the 
*Pfied of the armature, 
Md carries a four-lobed 
P"rnary contact maker 
/and also the secondary 
swrent distributor g. 
Pie- 34 shows the wir- 
'"ff connections. One 
™d of the armature 
Ending is grounded on 
the Qore, as usual, and 

fte other is connected 

t" the interrupter b, and 

through the wire h to the primary of the induction coil j. 

The other terminal of the primary is connected to the coil 
vibrator and also to the condenser j. A switch k has its 


blade connected with the other condenser terminal, and has 
the three contacts connected, respectively, to the vibrator / 
and the positive and negative terminals of the battery f«, as 
shown. The positive terminal of the battery is g^rounded. 

7 6. When the switch is in the position shown by the dotted 
lines, and the circuit is closed by the primary interrupter i, 
a charge of electricity passes through the wire A and pri- 
mary winding of the coil / into the condensery. As soon as 
the condenser is charged, which takes but an instant, no 
further current can flow, as there is no return to the 
grounded terminal of the armature. The circuit is then 
broken, leaving the condenser charged, and at the proper 
moment for the spark a contact is made by the timer /", thus 
grounding the wire A and permitting the condenser to dis- 
charge itself through the primary winding of the coil i, the 
flow being now in the opposite direction to that of the 
momentary charging current. The discharge of the con- 
denser is so sudden as to induce a very high momentary volt- 
age in the secondary winding of the coil. 

77. As one end of the secondary winding is connected 
to the primary winding, the secondary winding is grounded 
while the timer /is making contact. The other end of the 
secondary winding is connected by the cable n to the central 
terminals of the high-tension distributor^, whose arm/, 
Fig. 33, is secured to the rotating hard-rubber disk g 
attached to the shaft c. Four fixed terminals, mounted in 
the same hard-rubber piece r that holds the central ter- 
minal, distribute the current to the spark plugs. As the end 
of the arm p is widened, no advance is required in the dis- 
tributor, and hence the timer/, Fig. 34, is the only member 
moved to change the spark time, the condenser simply 
remaining charged, between the moments of contact, by b 
and/, respectively. 

As already slated, tlie battery furnishes current for start- 
ing, the switch /(' then being turned to the position shown 
in full lines in the diagram. The magneto is thereby dis- 
connected, and the battery current goes through the engine 


frame, contact maker y, wire A, primary winding of the coil, 
VT^brator ^ and the switch. The current can also go by way of 
tlie armature winding and interrupter b ; but, if the vibrator is 
adjusted for the current reaching the coil by the more direct 
route, it will not respond to the weaker current When the 
engine reaches normal speed, the switch is thrown over by 
the operator. The switch is of special design, and is very 
highly insulated to protect the operator from shocks. It is 
claimed that this magneto will produce a 3-inch spark in the 
^pcnair at 600 revolutions per minute, and a f-inch spark at 
50 revolutions per minute. As but a single spark is pro- 
dxiced, it can be timed with perfect accuracy. 


78t A magneto or djmamo requires little care except to 

*^« that it is mechanically in good order. The bearings 

sliculd be oiled at proper intervals, and the commutator 

touched now and then with an oily rag. The brushes 

should be watched to see that they bear evenly and with 

sufficient pressure to prevent sparking. Copper or carbon 

^ust from the commutator will gradually collect on the wires 

leading to the commutator, if these are exposed. So long 

^ it does not short-circuit the wires it does no harm, but it 

should be brushed off now and then. 

The distributor of a high-tension magneto is likely to pro- 
duce metal dust from the rubbing of the contact points, and 
^heu this lodges on the hard-rubber mounting it will in 
tinie lead to a short circuit from one high-tension terminal to 
^enext. It should be wiped off frequently with a slightly 
oily rag, and the film of oil left will serve the further pur- 
pose of preventing moisture from forming on the hard rub- 
^r, which would be as bad as the dust. On account of the 
%h secondary tension, great care is necessary to maintain 
Perfect insulation. 

'?9. All switches of magnetos should be heavily insu- 
lted. K necessary, a rubber tube may be slipped over the 


switch handle. As the current is very strong-, the shocks 
that might be recei\-ed by careless handling would be most 
violent. With magnetos of the type shown in Fig. 20, a 
secondary wire should not be disconnected and left where 
no spark can jump when the engine is running. This 
would put a severe stress on the insulation, which might 
ultimately break down. This is a good rule to follow with 
all jump-spark systems, both magneto and battery. 

Some high-tension magnetos work best with a smaller 
spark gap than is used with primary battery ignition, it 
being about one-half the length used with a primary battery. 
In the absence of instructions from the maker, the length of 
spark is best determined by trial. 


80. Knife switches such as are shown in Fig. 35 (a), {b), 
and (c), are commonly used in marine and stationary prac- 
tice. While the copper or brass used in them is liable to 
oxidation, they give the best service on motor boats because 
the action of opening and closing them tends to keep the 
contacts bright. The single-pole knife switch. Fig. 35 (a), 
has a detachable knife lever (7 that may be carried in one's 
pocket to prevent unauthorized use of the boat or automo- 
bile. There are three contact points *, r, and d. When the 
knife a is thrown in at *, connection is made with orue set of 
batteries, and with another set when thrown in at rfl When 
both batteries have been weakened through use, the blade 
may be thrown in at r, connecting the batteries in parallel 
scries and thus increasing the strength of the current deliv- 
ircd. What is known as a double-pole single-thnnv knift 
S7i'//i'/i is shown in Fig. 35 (d) ; while a switch of the same 
type but having a double throw is illustrated in Fig. 35 (c). 
Wires from two sets of cells or other sources of electric cur- 
rent arc connected to the poles of the switch beneath the 
])ase pL'itc, one set of wires leading to the poles a and ^, the 
other set leading- to the proles c and {l, connection with the 


external circuit being made through the posts e and f, in 
which the knife blades are pivoted. 

^1. Fig. 36 ia) and {b) shows the external appearance 
*''*1 system of wiring of a switch for use on automobiles 
'"" motor boats having single-cylinder or multi-cylinder 
^Sines, and with one oi' more sources of current. Thecon- 
^^t points of the switch, as shown in Fig. 36 {a), are 
*^anged so that, when the switch arm, or lever, attached 
'•* the post a rests on the button b, no current flows. When 
""f. one set of batteries is in use; when on d, the second 
Lti&iniise; when one, the batteries are connected up in 


multiple series, increasing their ampere capacity; and when 
on/, the batteries are connected up in series, increasing flw 
voltage. Fig. 36 {6) shows the switch wired for use witli 
two sets of dry-cell batteries A and Ji supplying current for 
the primary circuit of 
the spark coils C, from 
which the wires of the 
secondary circuit lead 
to the spark- plugs D of 
a four-cylinder engine. 
The binding screw a, 
Fig. 36 (i), for the . 
switch-arm post a. Fig. 
36 (a), is wired to the 
primary terminals of the 
coils C. From the car- 
bon plate of the right- 
hand end cell of battery 


A. a wire is carried to the binding screw c , tlie wire from the 
carbon plate of the right-hand end cell of battery B bdng 
carried to the binding screw f, under which is a link or con- 
tact strip s connecting »nth the contact points t/ and / 
Thus far, the some letters of reference apply to similar paitl 
in Fig. 36 {a) and (A). A wire from the zinc of battery A is 
connected to the bindingscrew^ attached to the metal plate il^ 

i 18 



A wire from the zinc of battery B is connected to the bind- 
ing screw i attached to the metal plate/. In a fiber plate k 
fixed on the post a, Fig. 3fi [n), so as to turn with it when 
the switch arm is shifted, are motmted throe contact pins/, 
tn, and « that slide on the metal plates // and j. These pins 
are electrically connected by means of a wire o laid in a slot 
in the fiber plate k and soldered to the pins. 

When the end of the switch arm rests on the contact point 
c, current flows from battery ,/ to c, thence through the 
switch arm toa, thence by wire/ tocoiis C, and by grounded 
connections J and r back to battery,'). When the switch 
arm is on d, current flows from battery B to e, thence 
through the metal plate s to d, through switch ann to a, to 
coils C, to grounds q and r, wire / to binding screw g and 
plate h, pin /, wire o, pins m and k, plate J, screw i, and 
wire u, back to battery B. When the switch arm rests on e, 
it also makes contact with the auxiliary contact point v. Fig. 
36 {a), which is connected to c. Fig. 36 {b), by means of the 
metal plate w. The two wires from the carbon plates of the 
right-hand end cells of the two batteries are thus connected 
together, the two wires from the zincs of the left-hand end 
cells of the two batteries being connected by means of the 
contact pins /, m, and «, wire o, and plates k and j. The 
batteries being thus connected up in multiple series, current 
Sows through binding screw e and switch arm to a, then to 
coils C, grounds y and r to battery vl, and to battery 5, by way 
of wire t, binding screw g, plate h, pins /, w, and «, and wire 
o, plate J, screw (', and wire a. When the end of the switch 
arm is shifted into contact with/, the pin /is moved out of 
contact with the plate h, while the pin « makes contact with 
the metal plate x, thus connecting the carbon of battery A 
to the sine of battery B, and thereby placing the batteries 
in series. Current then flows through the wire from the car- 
bon plate of the right-hand end cell of battery B to e, then 
through plate s to /, through switch arm to a, to coils C, to 
grounds g and r, back to the left-hand end cell of battery j4, 
thus completing the circuit. 

To prevent unauthorized use of the automobile or motor 


boat on which the switch is used, the contact post a is made 

82, Snap switches, the operative principle of whicJiia 
illustrated in Fig. 37, are commonly used for opening and 
closing the primary ignition circuit in stationary and maiine 
gas-engine practice. Fig. 37 shows a typical single-pole 
snap switch; the same type of switch is made double-pole — 
also, three-point and four-point. The wires from the bat-, 
tery or other source of primary current come through the por- 
celain base of the switch, and are held in posts a, b, which 

also carry the switch contacts. When the switch is closed, 
the rotary cross-piece c makes connection between posts a and 
b, thus closing the circuit. A double-pole switch has two 
pieces c and four contact posts. It is desirable to have snap 
switches provided with an indicating dial, as shown in 
Fig. 37 (fl), unless the position of the switch handle shows 
clearly whether the switch is "on" or "off," 

83, A switch for use with high-tension currents where 
two sources of current are available, as where storage bat- 
teries and coils are installed together with a magneto, is 
shown in section in Fig. 38. By throwing the switch han- 
dler to one side, the magneto- circuit is closed and the magneto 

g 18 


is in operation; throwing the switch handle to the other 
side cuts out the mag- 
neto, closes the bat- 
tery - and - coil circuit, 
and places the batteries 
and coils in operation. 
The ball contacts If are 
lield against the con- 
tacts c by the springs tf, 
and are in electrical 
connection through the 
strip e. Wires from the 
two sources of current 
are led to the binding fki,« 

screws y and ^, the common circuit-completinjf wire being 
attached at h. 



, The wiring diagram shown in Fig, 39 illustrates the 
metinid of wiring for a two-cylinder engine, the same 
scheme being equally applicable 
in making connections to multi- 
lylinder engines. When contact 
between the insulated and uninsu- 
lated electrodes of the igniter is 
made, current passes from the bat- 
tery a through one blade of the 
■frj- Y I switch b to the insulated electrode 

^ ' of the igniter </, then through the 

uninsulated electrode of the igniter 
to the grounded connection e, to 
the coil c, and back to the battery 
through the other blade of the 
switch b. 
85. Fig. 40 shows the wiring for a generator.or dynamo/, 
and one set of batteries. The spark coil c. Figs. 3i) and 40, 





is located between the ground on the engine and the switct 
The object of this is to provide means for connecting 




^^ — =* — vr- 



* I 


Fig. 40 

another set of batteries, using the same terminals as are used 
for the generator/. 

86, Fig. 41 shows two of the cylinders of a four-cylinder 
engine connected to one set of batteries, and the other two 



J « 



^ hCHI f HiliiiliH 

Fig. 41 

connected to a separate set. It should be noted that the bat- 
teries are so located as to make it easy to connect the cells 
so as to double the amperage when the batteries become 
nearly exhausted. 




87. Fig. 42 shows a double system of wiring for a four- 
cylinder engine with two coils and two sets of batteries. 
One coil could be removed by connecting the two points 
of the switches that are wired to the coils and placing 
one wire of a single coil in connection with the engine 

Fig. 42 

ground while the other is connected to the wire joining the 
two switch points. If both switches should happen to be 
closed at the same time, the current from both batteries 
would pass through the coil, and the amperage would be 
doubled but the voltage would not be increased. 

Pig. 48 

88. Fig. 43 shows double wiring throughout, for a four- 
cylinder engine, with a generator so connected up that either 
pair of cylinders may be operated by either of two sets of 



batteries a, a, or by a generator y, or all may be operated by 
both sets of batteries together, in case they may have become 

In connecting and setting up batteries successfully, it is 
only necessary to use a little thought, to reason out the com- 
plete circuit, which includes the engine ground, spark coil, 
batteries (or generator instead of batteries), switch, and insu- 
lated electrode. 


89. In wiring an engine for jump-spark or high-tension 
ignition, there are two general systems: In one system, the 
primary, or low-tension, current is commutated or alternately 
closed and opened, and in the other a so-called distributor is 
employed to close and open the induced, or high-tension, 
circuit for each of the cylinders. The object of this second 
system is to obviate the use of a separate spark coil for each 

The first is the system most in use. The positive or th^ 
negative poles of the coils should be connected together and^ 
wired through the switch, battery, and generator or direct — 
current magneto to a ground on the engine. If the positive 
poles are connected, each positive pole of the secondary wir — 
, ing should also be included in this connection, unless ther^ 
is a connection in the coil itself. Wires should be run fron:^ 
each binding post on the commutator to its coil. The wir^ 
should b2 well insulated, and of the same size and quality a^ 
used in make-and-break ignition. All joints should be made 
carefully, to be sure of good contact. The secondary wir- 
ing, which carries a current often as high as 30,000 to 40,000 
volts, should be specially made for the purpose, to avoid 
dangerous and faulty leaks of current. It should be as 
short as convenient, should be kept away from metal work 
of all kinds as much as possible, including parts of tjie 
engine, and should connect the spark plugs with their 
respective coils. There is so much more dampness (particu- 
larly around salt water) in boats than in automobiles that 


electrical losses due to leakage are more frequent in marine 
practice and have to be guarded against constantly, 

90. In wiring for high-tension distribution, the primary 
circuit is completed from a ground on the engine or uninsu- 
lated part of the distributor through the coil and battery, 
generator, or direct-current magneto, and to the single insu- 
lated binding post on the distributor. The secondary bind- 
ing post of the coil is connected to the primary, both being 
positive or negative ; and, by means of heavy special secondary 
wire, the other secondary pole is connected to the single sec- 
ondary binding post on the distributor, while secondary wir- 
ing connects each plug with its proper terminal on the dis- 
tributor. In connecting the secondary binding post on the 
coil, it is necessary to be sure that it is on the side leading to 
the engine ground rather than to the insulated electrode on 
the distributor. 

The wiring of a marine gas engine should be very care- 
fully done, particularly if the current is of high tension ; for, 
unless the very best material is used, and the work is done 
properly, there will be positive danger from explosion or fire. 
For this reason, manufacturers generally recommend make- 
and-break ignition when the engine is installed in a cabin 
or other enclosed space. Fire-insurance rates on such craft 
axe high, and risks are hard to place. 


91. High and low-tension wire cable, such as is com- 
monly used on automobiles and motor boats, is shown in 
Fig. 44 (a) and {b). The primary, or low- tension, cable is 
shown at (a). The wire core of the cable consists of forty 
strands of No. 30 tinned copper wire. The insulation con- 
sists of one layer of high-grade vulcanized rubber rt:, while the 
protective covering consists of two braids c and d covered 
with two layers of enameled coating baked on. It would take 
about 12,000 volts to puncture this insulation. The core 
of the high-tension cable (/^) is the same as that of the 




low-tension cable. The insulation consists of three layers of 
rubber «, b, c, vulcanized together. The rubber is protected^ 
by two braids e and /, covered with four coats of enamels 

'PiMi MMMH y///yy/^ / ////// ////// ///a/ ///v^ 


PIO. 44 

baked on in steam-heated ovens. The enamel forms a flexible 
insoluble film that protects the rubber from heat, oil, an 
water, the braid protecting the cable against mechani 
injury. More than 40,000 volts is necessary to puncture th 





1. Every automobile driven by an intemal-combiistion 
engine is provided with means for changing" the ratio of gear- 
ing, and for reversing, between the engine and the point 
where the power is used. The power is utilized at the rear 
axle, the rear wheels being the driving wheels. The engine, 
or driving, shaft and the driven, or propeller, shaft are sepa- 
rate, and provision is made between them for changing the 
speed and reversing by means of gears called speed-change 
gears. The reason for providing such speed-change gears is 
that the internal-combustion engine gives its highest effi- 
ciency when working with full charges. Consequently, it is 
desirable to operate the engine under those conditions as much 
of the time as possible, modifying the speed of the automo- 
bile by changing the gear ratio to suit the power actually 

Motor boats are generally provided with a reversing 
mechanism, having only one forward and one reverse speed. 

3, The automobile engine is proportioned and geared 
so as to drive the car at maximum speed on a smooth 
road when the throttle is fully open. If the road or grade 

QtfyriS^tdhy Initmatitmal Textbook Company. Entered at Stationers' Hall^London, 

1 19 


resistance increases, the car necessarily slows down to a 
point where the resulting reduction in the resistance of 
the air or wind offsets the increase in road or grade 
resistance, and if this speed of the car is insufficient for the 
engine to run properly the gear ratio must be increased to 
enable the engine to carry the load. This simply means 
that, while the engine speed is unchanged, the speed of the 
car is reduced by the change of gears. Every gasoline auto- 
mobile has at least two choices of gear ratios for forward 
motion, in addition to a single slow-speed reverse-gear move- 
ment. In the higher-powered cars, three and often four 
gear changes are -provided, by which means the engine may 
always be run at approximately the most advantageous speed 
to get the power it is capable of developing. These gear 
changes are convenient also when it is desired to run the car 
slowly, since even with the best carbureter and the best engine 
design, it is impossible to run a gasoline engine effectively 
below a certain speed, which is generally between 200 and 
400 revolutions per minute. If a lower car speed is desired 
it is obtained by using one of the lower speed gears. 

There are in common use three systems of speed-changing 
gears, commonly known as transmission gears ; namely, 
the sliding'gcar system^ the mdividual-clutch systetn^ and the 
planetary system, 


3. In Fig. 1 is shown a plan view, with body removed, 
of a small touring car equipped with a four-cylinder gaso- 
line engine a and sliding-gear transmission b. From the 
speed-changing gears the power is transmitted through a 
jointed propeller shaft c and bevel pinion and gear, enclosed 
at d^ to the rear axle e. Attached to the engine shaft is the 
flyi\'heel / carrying a friction clutch, and just back of the 
clutch is a coupling g connecting the clutch with the speed- 
changing gears. At // is a brake; at/ and/ are universal 
joints, which will he described later; and at k and /are hub 
brakes. In this transmission system the drive is direct^ as it 



is called, in the high-speed gear. In the slow and interme- 
diate gear positions, generally called the first and second 
gears, the power is transmitted from a pinion on the engine 
shaft to a gear on a lay shaft, or jack-shaft, and from a pinion 
on the lay shaft back to a gear on the propeller shaft in line 
with the pinion first mentioned. 

In Figs. 2, 3, 4, and 5 is shown a sliding-gear system with 
three forward speeds and one reverse speed. The coupling 
shown at a. Fig 2, connects the short shaft b to the engine 

shaft, while the coupling c at the other end connects the 
short shaft a' to the propeller shaft The shafts b and d are 
separated close to the gear e, which is ke)wd to the shaft b 
and has a portion of a coupling on the side toward the gear/ 
to which is connected the other portion of the coupling. 
The gears _/'and g are fastened together by a sleeve that 
slides on a feather in the shaft d; it should be noticed that 
the gear /is smaller in diameter than the gear ^. The lay 
shaft h carries the gears /, /, and k that are keyed to it and 
the gear /on a sleeve that slides on a feather. The gear k 
is slightly smaller than the gear/', so that, when the gear ^ is 
moved to the extrenre right, it does not mesh with k but 


vith a small idle pinion m that is in mesh with i. A brake 
3 shown at n on the shaft d. 

4c, In the position shown in Fig. 2, the transmission sys- 
lem is set for the slow forward speed of the car; the gear / 
s in mesh with the smaller gear e, reducing the speed of the 
ihaft A, while the gear / meshes with the larger gear g, 
igain reducing the speed so that the shaft d turns slower 
than k and much slower than the shaft b. 

In Fig. 3 the gears are shown set for the intermediate 
forward speed, with the gears e and / still in mesh; but the 
gear (', which is larger than the gear J, is in mesh with 
the genrf, which is smaller than the gear^. Consequently, 
the speed reduction from the shafts to (/is less than in the 
case shown in Fig. 2. 

I n Fig. 4 the gears are set for the high forward speed. The 
gear / has been moved out of mesh with the gear e, and the 
sleeve carrying /and ^ has been moved so that the clutch 
on /engages with that on gear e and the two shafts h and <f are 
locked together and turn as one shaft, there being no gears 


in mesh. The propeller therefore rotates at the same spe^= 
as the engine shaft 

In Fig. 5 the gears are shown in position for the revere 

motion. The gears e and / are again in mesh, bat the gear^ 
is in its farthest pnsitinn to the right and in mesh with the 


idler m that is behind and in mesh with the gear k. Conse- 
quently, the shafts b and d turn in opposite directions, and 
the propeller shaft runs at the reverse speed, giving a back- 
ward motion to the automobile. 

To avoid shocks in changing gears, the coupling a^ Fig. 2, 
is not connected directly to the motor shaft, but is connected 
to one member of a friction clutch partly enclosed in the fly- 
wheel, shown at/", Fig. 1, and this clutch is invariably 
released before changing gears. In this manner the shock 
involved in changing gears is confined to that necessary to alter 
the speed of the gears themselves and of the part of the clutch 
connected to a. Fig. 2. The gears are made of a special 
tough steel suitably treated to enable them to withstand this 
shock. As a single clutch is used for all speeds, it is made 
with a very large surface, so that the wear on it is almost 

iNi>iviDrrAi.-ci.rrTcn tra.nsmis.sion ststem 

6. In the individual-clutch system there is a separate 
friction clutch for each speed. In Fig. G is shown a system 
with two forward speeds and one reverse. The flywheel a 
is keyed to the engine shaft and is connected to the shaft b 
by the coupling c. From the shaft ^, motion is transmitted 
to the propeller shaft d through the different clutches and 
gears. Keyed to the short shaft b are the gears e and/* and 
the friction cones ^ and //. The gear /and the clutch disk/ 
are parts of the same piece, which is provided with a bush- 
ing k that fits loosely on the shaft b and is free to rotate on 
the shaft. The collar / is loose on the shaft b and can be 
moved by the lever m so as to force the end of the dog // 
against the friction plate o and thus force the pin p against 
the cone g. 

On the lay shaft q is keyed the gear r, but the gears s 
and /, which are provided with bushings, fit loosely on the 
shaft. The friction cones // and v are keyed to the shaft q, 
as are also the friction plates w and x. The col- 
lar y also fits loosely on the shaft q and operates on the 


dogs z and ^,, throwing one or the other of them against its 
friction plate and putting that gear into operation. There 
is a small idle gear that stands behind but meshes with 
the gears / and e. There is also a brake band at a^^ 
that may be used to prevent i and j from turning, or to 
bring the moving parts to rest. 

6, In the position shown in Fig. 6, the collar / has 
pushed out the long end of the dog n and forced the friction 
plate o against the pin/, causing it to force the cone g into 
the gear % and the clutch disk j on the cone A, thus locking 
the shafts b and d together. Consequently, the propeller 
shaft turns with the same speed as the engine itself, which 
is the highest speed that is transmitted. When the collar / 
releadles the dog «, the cones g and h are disengaged by the 
pressure of the small springs shown in the hubs of these 

When a slow forward speed is desired, the collar y is 
forced to the right, moving the long arm of the dog z^ out, 
forcing the friction plate x against the gear j, and the gear 
on the cone v. Consequently, motion is transmitted from 
the shaft b to the shaft q by the gears / and s and the fric- 
tion clutch V. From the shaft ^, motion is transmitted by 
the gear r to the gear i and thence to the shaft d. It should 
be noted that, as the gear f is smaller than the gear j, the 
shaft q turns more slowly than the shaft b, and, as the 
^ar r is smaller than the gear f , which is rigidly attached 
to the shaft rf, the shaft d turns more slowly than the 
shaft q and therefore much more slowly than the engine 

When the collar y is thrown to the left, the gear / is 
locked to the shaft, and, on account of the intermediate gear 
l>etween / and e^ the propeller shaft d turns in a direction 
opposite to that of the engine shaft — that is, the motion is 

It should be noted that the gears s and / ordinarily run 
loose on the shaft q and turn the shaft only when held by 
the friction clutches. As these gears are constantly in mesh 




with the gears e and /keyed to the shaft b, they produce 
unavoidable friction, as do also the friction clutches not 
engaged. On account of the unavoidable friction of the 
constantly meshing gears, and also the dragging of the 
disengaged clutches, this system is not verj- much used. 



7. Another speed-change system often used is knowf 
the planetary system. It comprises a high-speed connec- 
tion for the direct drive, and an arrangement of gears that 
reduces or reverses the motion when one or another drum 

on which these gears or pinions are mounted is held stB 
ary. Most planetary systems give only two forward spi 
and one reverse, but in some instances they are made to 
give three forward speeds. They are used chiefly on small 
automobiles, or runabouts; but when cheapness of construc- 
tion is an object they are sometimes employed on touring cars. 
In Fig. 7, is shown one form of planetary system. The 
gear a is the only one keyed to the engine shaft h. The 
gears c, d, and e all mesh with the gear a, and are made 
long enough to extend beyond a and mcsb with tJis geais 


/i ^, and h in pairs. The last three gears in turn extend 
"boyond the gears c^ d^ and e and mesh with the gear i^ 
iwliich is keyed to a sleeve connected to the drum j. The 
grears Cy dy e^ /, g^ and // turn on pins fastened to the 
dnim ky but only the gears r, rf, and e mesh with ^?, and 
only y, ^, and h mesh with the gear i which turns loosely on 
the shaft b. The internal gear / meshes only with the 
gr^ars Cy dy and e^ and is rigidly connected to the sprocket m 
that drives the automobile. The cover n is attached to the 
^ace of the drum k by means of screws, thus forming an oil 
reseirvoir that keeps the gears well lubricated when the 
fi-utornobile is running. There are separate brake bands 
aroimd the drums/ and >&, and a friction disk keyed to the 
shaft just outside of the drum/. 

W'hen the friction disk is pressed against the drum/, the 
Z^^T i is held so that it must turn with the shaft; conse- 
quently, the entire mechanism is locked together and the 
^rocket tn turns at its highest forward speed. If now 
the friction disk is released and the brake band around the 
^rurn / is applied so as to hold it from turning, then 
the gre^f ^ turns the gears Cy dy and ^, causing them to turn the 
g'^ars/, gy and h ; but, as the gear i is held stationary with 
the drum/, the gears/", gy and //, and also the drum ky to 
^hiQ"h they are attached, must revolve around the gear i in 
the same direction as the shaft turns, but more slowly. The 
S^^Ts Cy dy and e turn on pins that are fastened to the 
^^^m k\ consequently, they revolve with it as they turn on 
^heir axes and thus cause the internal gear / ^nd the 
Sprocket m to turn in the same direction as the shaft. This 
S^ves the slow forward speed. 

When the drum/ is released and the drum k is held by a 
^*^e band, the gears r, dy and e are caused to turn on their 
Ittns, and consequently drive the internal gear / in a direc- 
tion opposite to that of the engine shaft, driving the auto- 
mobile backwards. When the brake bands and friction disk 
are all free from the drums, the gears turn idly, and if the 
engine is running, no motion is transmitted to the sprocket 
and the automobile stands still. 




8, In motor boats, it is often desirable to run the pro- 
peller backwards even when there is only one set of gean 
for forward speed and hence no speed-change device. In 
such cases, it is desirable to have a device by means of 
which the direction of motion of the propeller shaft may be 
reversed while the engine runs continually in the one direc- 
tion. The reverse motion of the propeller is sometimes 
needed to check the forward speed of the boat, to bring it 
to rest, or to run it backwards. There are several forms of 
snch reversing mechanisms, but they are all similar in prin- 
ciple so far as the motion of the engine and propeller shaft 
is concerned, differing only in the method of making tbe 
connections for the reversal of motion. In some cas 

gears and clutches are iisfd ; in others, spur gears and slid- 
ing feathers; and in stiH others, bevel gears. 

In Fig 8 (a] is shown a reversing gear that depends oa 
friction clutches for its operation. The propeller shaft is 
divided into two parts, the one connected to the propeller, 
carrying the gear a, and the other, connected to the engine, 
carrying the gear d. The gears c and f^ mesh with these 
gears, and it should be noted that the gear b is slightly 
smaller than the gear a and that c meshes with 6, and J 

§ lo 




^v'i 1 1:1 a. Another gear similar to f, but not shown, meshes with 
^/ a-ncl d, while one similar to i/ meshes with a and c. The 
g^SLirS'C and ^nm on pins that are held in place in the web 
^f "ttie drimi e. 

T^liere are two friction clutches y* and ^'', the latter serving 
tc> hold the drum e stationary when the movement of the 
P'i*op>eller shaft is to be reversed. To reverse the motion of 
ttk^ propeller shaft while the engine is running, the spreader 
^' is thrown inwards by the reverse lever, so that the 
d'*"it:c:h^, which is stationary, grips the drum e and holds it. 
'^h^ pins on which the gears c and d revolve are thus also 
^^l-d stationary, and the relative motions of the gears are as 
s^ c>^wn diagrammatically in Fig. 8 (b). The crank-shaft trans- 
mits motion to the gear d, in the direc- 
tion indicated by the arrow. The gear c 
in mesh with b turns in the opposite direc- 
tion and transmits motion through a long 
gear c\ not shown in Fig. 8 (^), to the 
gear a on the propeller shaft, which is 
thus made to move in a direction oppo- 
site to that of the gear d on the end of 
the driving shaft. The gear d is also in 
mesh with the gear d\ which turns gear 
d in the same direction as that in which 
the gear c^ moves, and hence helps to 
gear ^ in a direction opposite to that in which the 
^^^Aring gear b moves. The gears d' and ^are duplicates of 
tri^ ^ears c and c\ each pair transmitting a portion of the 
^^^^-v^er when the lever is reversed. When the reverse 
^P^^aderA is thrown out of engagement and the fon\'ard 
^P^^ader i is thrown in, the same movement of the reverse 
'^^'^^T serving to accomplish both operations, the clutch / 
^^I>s the drum e, which is thereby caused to rotate with the 
^^VTiig shaft to which the clutch/ is keyed, all the gears 
^ing locked together. The gears therefore have no 
Tel^t{yg motion, and the whole mechanism, including the 
Propeller shaft, rotates at the speed of the driving 

7 10. 3 id) 


9, A somewhat different type of reversing gear is shown 

a Fig. 9. The driving shaft a is connected directly to the 

[ propeller shaft b by the clutch coupling c in the position it 

I now occupies. In this position the gears d, e, BnA/Aa not 
transmit power, but the gear / turns idly on the propeller 
shaft By throwing the clutch coupling to the other side, 
however, the shafts are disengaged and the clutch holds the 
gear/ rigidly to the shaft b, and the direction of rotat joglt 




10, • Differential gears are composed of a set of four or more 
gears attached to the ends of two shafts that come together 
and are usually in line, so that both are rotated in the same 
direction; but if either meets with extra resistance it may 
rotate more slowly than the other or may stop altogether. 
These gears are used on the driving axles of automobiles. 
The axle is made in two parts, with a gear on the end of each 
where the parts come together; other gears mesh with both 
these axle gears and are driven from the engine by a 
sprocket and chain or by bevel gears and shaft. These 
gears turn the axle, but permit its two parts to turn in 
respect to each other so as to allow the automobile to go 
around a comer without causing the wheels to slide or skid. 
The rear wheels are each fixed to a half of the rear axle, and 
both receive power, hence it is necessary to allow one wheel 
to turn at a different speed from the other; this is done by 
the differential, or, as it is sometimes called, the compensate 
ing or equalizing gear. 


11. A spur-gear differential is shown in Fig. 10 with 
the ends of the two shafts, carrying the gears c and d. 
The sprocket wheel e is driven from the engine by a chain, 
and is in turn fastened to a gear-case that carries a series of 
small gears f, g^ arranged in four pair, each gear being 
mounted on its own axle. The two gears of each pair 
mesh together, and one is in mesh with gear c while the 
other meshes with gear d. By this arrangement both 
gfearsV and rfare drawn in one direction, and yet they may turn 
•with respect to each other when the resistance to the turn- 
ing of one is gfreater than that of the other. When the 


that for the spur-g«ar differential. When both gears meet 
with the same resistance, the small bevel gears d do not 
turn on their bearings; but when the movement of one of 

the gears e or f is resisted more than that of the other it 
lags behind, causing the small bevel gears to turn on their 
axles sufficiently to cause the resistance to be equalize. 




13. Plain CoupllnKB. — Several plain couplings, such a3 
ate used on propeller shafts of motor boats, are shown in 
Fig. 13 {a\ (b\ and fr). The one shown in Fig. 12 {a) holds 
the two ends to be coupled together by means of setscrews 
through the holes shown in the sides of the coupling. In 




the one shown in Fig. 13 (6), the ends are clamped by means 
of bolts, one end of the shaft being in one end of the coupling 
and the other in the opposite end of the 
coupling. In Fig. 12 (c) is shown the 
flange coupling, one-half of which if. 
keyed to each end of the shaft so that 
the separate shafts are held together by 
means of bolts through both flangea 

1.4:> Compression Couplln^r- — A 

modified type of flange coupling, known 
as a coHifrcssion coupling, is shown 
in Fig. 13 ((z) and {b), (d) showing 
ihe separate parts and ip) the assem- 
bled coupling. In this coiipling no 
keys are used, but a loose sleeve a. 
Fig, 13 (i7), fits over the ends of the 
two parts of the shaft to be coupled; 
the sleeve is tapered on the outside 
toward both ends and has six slits, 
three from each end, equally spaced 
The loose sleeve a is first slipped in 

around the sleeve. 

r the shaft and liien the parts b and c are bro-jght 


sleeve on the two parts o£ the shaft, owing to the taper on 
the sleeve, holds them togetlier. 

15. Universal Coupling. — It is often desirable to have 
the propeller shaft so constructed that ooe part may stand at 
an angle to the other. This may be done very conveniently 
by means of a nnlversal Joint or coupHiiKt sometimes 
called a crab claw, shown in Fig. H, The shaft a is con- 
nected to the shaft b by the coupling shown at c. Two forks 

V\0. 14 

(/and e are connected to the shafts; on the ends of the forks 
are balls /and ^, which tnrn in cups that are fastened to the 
casing A, which turns with the forks. Each fork is thus per- 
mitted free motion at right angles to its shaft. A coupling 
of this type permits the shafts to turn freely so that power 
can be transmitted through the two shafts at a slight angle 
almost as readily as through a continuous shaft 

When the power must be transmitted from one of two 
parallel shafts to the other, the two must be connected by a 
third, or intermediate, shaft with a universal coupling at 
eadi end. In order that the motion of the driven shaft may 
be the same as that of the driving shaft, the forks on the 
intermediate shaft must stand in the same plane. 


16. Cone Clutches. — The clutches commonly nsed on 
the power-transmission mechanism of automobiles and motor 
txiats may be divided roughly into three classes; namely, cone 


clutches, band clutches, and disk clutches. They are s 
designed to permit the engine to be disconnected from tK 
transmission gearing, either while the gears are being shifte 
or when the machine is to be stopped. 

The cone clutch is provided with a cone-shaped memb- 
attached to one part of the shaft, and a tapered ring or cu_ 
into which it fits. When the cone is forced into the rin 
both shafts are held firmly together by the friction of t^ 
conical faces. 

There are a number of modifications of this t3rpe of clutc= 
one of which is shown in Fig. 15. The flywheel a is fi 

to the shaft b by means of bolts through the web of t*^ 
wheel. At c is shown an expansion ring into which ^"^ 
friction cone d fits. The helical spring e holds the co"^ 
against the expansion ring with the required amount o\ 
force. At /is a ball bearingthat takes the end thrust wh^" 
the cone '\^ pulled away from the expansion ring. Tt** 
arms .ifare coii])le(l to the propeller shaft that turns v " 


§ IS 



tlie friction cone. Ordinarily, the two parts of the clutch 
ar^ held together by the pressure of the spring, and when 
it is desired to disconnect the cone, as when the speed 
is Toeing changed on an automobile, a foot-treadle is forced 
down so as to act on a fork and sleeve and pull the cone away 
from the expansion ring. As soon as the treadle is released 
the spring e forces the clutch into action again. 

"17. Band Clutch. — Another type of clutch known as 
the band, or frlctlon-rlng, cluteli is shown in Fig. 16. 

FlO. 16 

I he wheel, which is connected to one of the shafts, is shown 

^^ ^, and the band or ring, which is connected to the other 

^^aft, and which is made in two parts, is shown at b and c, 

^^ d and e are curved arms pivoted at / and g. The links // 

^^d j" connect these curved arms to the parts b and c of the 

"^^nd. By means gf a fork and tapered sleeve, not shown, 

l^e ends/ and k of the arms are forced apart when the clutch 

is brought into use. This throws toward the shaft the 

^^ds / and m of the levers d and e, and brings the two parts b 

^^^ c of the clutch ring in contact with the friction or driv- 

i"? surface of the wheel a, which is thereby forced to turn 

^ith the driving shaft 



18, Disk Clutch. — A clutch of the multiple -disk type i s 
shown in Fig. 17. A two-arm spider a keyed to the shaft ^ 
serves to hold in place a number of metal disks ^, betwe^sn 
which are other metal plates d held on the sleeve f by mea.:i:».s 
of a key/! The sleeve eis in turn keyed to the shaft/; a-X3<3 
to it is screwed a ring A having three pair of lugs carryiir^s 
three levers i with rollers_/' at their outer ends, as shown. TT^a.* 
other ends of the three levers press against the plate i wh.^M 
the clutch is engaged byan inward movement of the collac" ^, 

the plate i being free to move along the key^l The dislesf 
are free to move longitudinally on the arms of the spidex"./ 
and also on the sleeve c, around which they rotate when, t Jie 
clutch is out of engagement; but the arms of the spid^f. 
fitting into slots in the disks, cause them to rotate with t*"^ 
shaft d. The plates d are free to move longitudinally d 
the key y in the sleeve c; and since the sleeve is keyed to tfie 
shaft j^, it is evident that, when in engagement with tli^ 
disks f, the plates d must cause the shaft £- to turn wi tf* 
the shaft b. The disks c and the plates d run in an oil batl^' 
obviating wear of the plates and disks. These are broug'ti* 
together forcibly by throwing the cone-faced end of the coll^*" 
/ against the rollers /, thereby causing the ends of the thr^* 
levers / to press the plates and disks together with sufficiei^' 
force to cause the shafts * and ^ to rotate as one shaft. 





19. The power- transmission system of an automobile is 
usually fitted with one or more brakes. The most common 
arrangement is to have a brake on the propeller shaft and 
one on the hub of each of the rear wheels. The brake may 
be of the expanding type 
placed inside some wheel as 
a flywheel, or it may be on 
the outside of a wheel, in the 
form of a band. The band 
brake is often applied to the 
hubs of the rear wheels and 
is operated by means of a 
treadle. A rear-hub brake 
is shown in Fig. 18, with the 
hub at a and the brake band 
at b. The connecting-rod c 
from the treadle to the lever d tightens the brake by draw- 
ing the link e down and shortening the brake band b. The 
lug f is held from turning with the hub by the arm that 
extends from the axle casing to the pin g. Releasing the 
treadle allows the rod c and the lever d to move back and 
thus throw off the brake. 





20. The most common method of starting automobile 
unftincs is by. means of a simple hand crank that can be con- ' 
necteil to the engine shaft and by means of which the shaft 
(.'iin hv turned by hand until a charge is dra^v^ into the 
cylinder, compressed, and 
ignited. Some cranks are 
made so that they will dis- 
engage as soon as the engine 
starts, and also so that, 
should the engine explode 
a charge and start back- 
wards, the backward mo- 
tion, frequently called a 
l-ii:k, will not injure the 
oiDcrator. A crank of this 
type is shown in Fig. 19. 
The handle a is connected 
to the end of the long 
sleeve A by the pin or latch 
<-, which is held in one of 
a number of equally spaced 
slots in the end of the sleeve 
The ratchet wheel c is 
.iu:i.':;iobile and is thus held 
'I s;:rKo:ent siie to permit the 
led .i:-.,'. fitted to the cranfc- 
r.otchos of the ratchet whee\ 

iiio the crank at .; 



and is rigidly connected to the lever ^. The pin h and the 
spring I hold the lever g against the pin /, which is fast- 
ened to the latch c, and also hold the pawl _/"down to the 
ratchet wheel. The slot k in the sleeve fits on a pin in the 
cranlt-shaft of the engine, so that as the crank is turned in 
the direction of the arrow it turns the crank-shaft, but it 
canaottum the crank-shaft in the opposite direction. If 
the engine should kick backwards, the pawl / would be 
stopped by the teeth of the ratchet e, and in turning would 
'^ise the lever ^, lifting the piny and the latch r, thus per- 
"lilting the sleeve b to turn freely without carrying the 
fandJe with it. 


Si, In Fig. 30 is shown a small hand air pump that is 
attached to the side of the car near the driver's seat. The 


cylinder a is of rather large diameter, the piston rod b car- 
ries a handle c of convenient size, and the pump is placed in 
the most convenient position for the driver to operate with- 
out leaving his seat. The object of the pump is to com- 
press air for starting, the air passing over gasoline in the 
surface carbureter d on its way to the valves e through 
which the starting charge is admitted to the cylinders. To 
start the engine, the valves e and compression relief cocks/ 
are opened by means of the operating handle g" attached 
to the rod A, the driver gives the pump plunger a few 
strokes, and the air is driven through the carbureter d to 
the explosion chambers of the engine cylinders. The 
charge is then ignited and the engine started. Air for 
the compressor is drawn into the pump cylinder a on the 
up stroke through the flap valve /, and is expelled on the 
down stroke through the outlet valve j\ which is seated 
by a spring, as indicated. Simultaneous operation of the 
relief cocks and charging valves is effected by connecting 
the rods k and / to the lever m attached to the rod A. 


22. Marine gas engines are usually started by hand. 
Some four-cylinder marine engines, however, are equipped 
with air starting and reversing mechanism, one type of 
which is shown in Fig. 21. This mechanism consists of a 
hand bicycle tire pump, two check- valves, a priming cup, 
piping to the two after cylinders, and stop-cocks therein. 
A plain lubricator a is used as a priming cup, b, b are two 
check valves, c is the tire pump, d and e are stop- valves 
that are sometimes placed at /, /, and g^ g are the two after 
cylinders, that is, the two cylinders toward the stem of the 
boat — of a four-cylinder engine. The priming cup is partly 
filled with gasoline, which is allowed to run into the base of 
tHe pump. The engine is turned over by hand until the 
piston has slightly passed the upper center and the igniter 
has snapped. The piston in the other cylinder will now 
have begun to start on its compression stroke. The valves 




d and e are opened, and pressure is pumped up in the 
two cylinders. The valves are closed, and the igniter in 
the cylinder with the piston just past the upper or outer 
center is snapped by the finger, when, if the proportions of 
the charge in the cylinders are correct and all other condi- 
tions are right, the engine will start. The advantage of a 
compressed-air starting and reversing mechanism for start- 
ing the engine in either direction lies in its small size and 

PIG. 21 

low first cost. In operation, different sets of cams and 
usually auxiliary air valves are employed to control the 
movement of the engine.* In six-cylinder engines, only 
three of the cylinders are equipped with the air attach- 
ments, the other three taking up their cycle of operation 
when the mixture ignites, whereupon the compressed air is 
shut off and the regular inlet- and exhaust-operating cams 
come into operation in place of the air-valve operating cams. 
With some large engines, a smaller engine is sometimes 
employed to start the larger, the small one being discon- 
nected as soon as the larger one starts. 





23. Automobile engines are controlled by manipulation 
of the throttle valve and the position of the spark, some- 
times called the spark lead. More accurately, the control 
proper is accomplished by regulation of the throttle, and 
the spark advance is regulated to keep the ignition at its 
most advantageous point for developing the maximum 
power of the charges received. 

The manipulation of the spark is sometimes employed to 
modify the speed of the engine, because, with the spark 
retarded to cause ignition to occur later than it should, the 
power of the motor is very materially reduced. This, how- 
ever, is a most objectionable practice for several reasons: 
In the first place, it evidently wastes gasoline, because the 
same result as regards power may be obtained with smaller 
charges and an earlier spark. Second, the inflammation is 
so prolonged that it probably is not completed at the time 
the exhaust valves open, so that the valve seats are exposed 
to streams of gas still burning. This not only overheats 
the valves and is liable to warp them, but it soon burns and 
cuts their ground faces and their scats. Third, the motor is 
overheated dnd preigiiition of the incoming charge may 
result, producing explosions in the carbureter and intake 
pipe. It is, however, permissible to retard the spark to 
prevent racing, that is, running too fast, when the throttle 
is nearly closed and the motor is running light, with the car 
standing still. 

24. Since automobile motors are operated under wide 
variations of speed and load, it follows that for correct 
action the throttle and spark cannot always be operated 
together For example, a rarefied charge, such as is 
obtained with the motor at medium speed, with 
the throttle nearly closed, will bum comparatively slowly 


aricl requires an advanced spark for its prompt combustion. 
Suppose, now, that the car is running at moderate speed 
under these conditions, as it may when descending a slight 
grade, or even on level ground. If a slight up grade is 
encountered, the operator will open the throttle to increase 
the power. Under such conditions the speed of the motor 
will probably not increase, but it will be found that the 
spark advance suitable for the previous conditions is too 
early for the increased charges. This will be indicated by 
the laboring sound and possible pounding of the motor, 
either of which sounds may be stopped at once by slightly 
retarding the spark. 

If the throttle and the spark mechanism were positively 

connected, it would be impossible to advance the spark 

while closing the throttle, as was required for the first set of 

conditions, and to retard the spark while opening the throt- 

^^^, as was necessary for the second set of conditions. 

-Although having the two positively connected simplifies the 

pperation of the car in the hands of the novice, and although 

'^ is undoubtedly satisfactory under some conditions, as for 

example when the car is speeded along a level road, it is 

'^^t flexible enough to give the most favorable results in 

Either speed or fuel economy. 

A simple automobile governor acting on a throttle 
^"^Ive located in the intake pipe is shown in Fig. 2'2. The 

yl^alls a, a are revolved about the engine shaft b and fly 
^Ut^vards against the resistance of the spring c under the 
^^^ion of centrifugal force. The fly balls move the sleeve d 

^t. Wards as the speed of the engine increases and inwards 

^ it decreases. The rocker e pivoted at/ moves with the 
^le^ve ^ and transmits its motion through the rcxl^to the 

^^ottle valve // in the supply pipe /". 

^6. Small engines are commonly controlled entirely by 

^^d, there being no centrifugal governor on them. 

"^^tiiost all automobiles with four-cylinder engines of 

*^ liorsepower or more have centrifugal governors, whose 

^Unction is partly to prevent the engine from racing when 


the clutch is released, and partly to facilitate the control of 
the automobile by making the engine semiautomatic in iu 
speed regulation, thus relieving the operator of part of the 



attention to the throttle, otherwise necessary. When the 
centrifugal governor is employed, it is always arranged to 
be modified in its action by the operator. This may be 
accompliHhed in several ways, of which the simplest is to 
open or close the throttle forcibly against the resistance of 
the governor mechanism. This may be done by running a 
connection from the long upper arm of the governor lerer 
to suitable controlling mechanism under the operator's 
hand. The usual connection would be a slotted link, 
attached to the governor lever so as to permit the governor 


flyl)alls to approach each other but not to separate, and 
would therefore limit the degree to which the throttle was 
pexTnitted to close. 

27. A'more elaborate arrangement than that shown in 
^i& 22 is shown in Fig. 23. It has the special feature that 
the hand regulating device imposes no stress on the governor 
niechanism, and friction and wear due to this cause are 
^lixninated. The fly balls a of the governor revolve around 
the engine shaft by their outward motion being resisted by 
^o spring c. The sliding collar d and governor lever e act 
^i>. the throttle arm / through a slotted link g, and as the 
flyl>alls separate, this link is simply shifted to the left and 








Pig. S8 

the throttle is closed by the tension of the spring A. The 
^nd regulation is effected through the rod i, which works 
freely in an army connected to the throttle arm, and has an 
^instable nut and locknut at its end, by means of which 
^^ throttle may be pulled open against the tension of 
^P'^ng A. When the throttle is thus forcibly opened, the 
^^t in the link ^permits the governor mechanism to remain 
^ its natnral position, as determined by the speed of the 
^Rine. As i is rigidly connected to the hand control lever. 


the effect is to limit the degree to which the throttle can 
close, this restriction being independent of the action of 
the governor. Consequently, if the rod / is pulled to the 
right as far as it will go, the throttle is held wide open. 


28, Governors are not used on marine engines to any 
great extent Several makers of engines up to 100 horse- 
power or more have never adopted them, or have dis- 
carded them after several trials. Small engines rarelv have 
them, except when used for some special purpose. When 
governors are used they are almost always of the throttling 
type, similar in principle to those used on automobiles. 

The governors in use are usually within the flywheel, or 
are mounted on the throttle valve and operated by a belt 
from the crank-shaft, and are of the centrifugal type. 

They are quite convenient when using a reversing gear, 
but very many engines have been wrecked when too much 
dependence has been placed on the governor and it has 
failed to act, as, for instance, through the breaking of a belt 
or spring or a stud carr^^ing the lever arm. 

If the engine is of the automobile type with very light 
reciprocating ])arts, it gathers headway more rapidly than a 
heavy lo\v-six.'ed engine, and for this reason is much more 
likely to be wrecked should a governor fail to work 

It is an excellent plan to have a switch in the battery cir- 
cuit convenient to the steersman, so that the current may be 
shut off should an emergency of any kind develop that 
would necessitate suddenly stopping the engine. Some 
cn^i^'incs are so installed that they may be handled from two 
or more parts of the boat, and in this case the danger 
rcfcn*ed to would be considerably lessened. 





29. Marine engines are cooled by the circulation of 
water through the water-jacket of the engine cylinder. A 
pump attached to the engine draws water through the bot- 
tom of the boat, sends it to the engine, and finally dis- 
charges it into the exhaust pipe, which is sometimes led 
under water, discharging through a special fitting, one form 


Fio. ^ 

of which is shown in Fig. 24 (a). The exhaust enters the 
fitting at a and leaves at ^, under the water, the boat mov- 
^S m the direction of the arrow. On account of the veloc- 
^ of the boat, water rushes into the opening c, through 
^® gradually reducing passage, into the exhaust pipe, and 
o^t with the exhaust at d. This arrangement tends to 
increase the velocity of the exhaust and reduce the back 
pressure on the engine. 

Another form of exhaust nozzle is shown in Fig. 24 (^). 
This form resembles that shown in Fig. 24. (d:), except that 
the passage c is omitted. 



30. In automobiles, the circulating system is open to the 
atmosphere, and it is important that the water used for 
cooling should not be allowed to boil, because it wotdd 
soon be exhausted. Since it is impossible to cany a 
large supply of water, it is necessary to use coolers, or 
radiators, as they are called, through which the water is 
circulated, and which have a large metal surface exposed to 
the air. 

Owing to the considerable amount of power developed 
by many automobile engines, and the necessarily small 
amount of cooling water that can be carried to sup- 
ply them, highly efl&cient means must be adopted for dis- 
persing the heat as fast as it is received by the water. As 
the only way of accomplishing this, without the evaporation 
of the water, is to give the heat to the air by convection, it 
follows that the logical method of cooling the water is to 
spread it in as thin sheets as possible over metal surfaces 
exposed to free currents of air set up by the movement of 
the vehicle, by a suitable fan, or by both. 

31, In a few makes of cars of moderate power, gravity 
circulation alone is relied on to keep the water in motion. 
In this case the bottom of the radiator should not be lower 
than the bottom of the water jacket, and the top of the 
radiator should be as much higher than the top of the jacket 
as conditions will permit. The arrangement of the piping 
for gravity circulation is shown in Fig. 25. The vertical 
radiator tubes ^, a are connected at top and bottom by mani- 
folds b^ c, or chambers with suitable connections for the 
pipes. The water leaves the top of the water-jackets rf, d, 
enters the manifold b, descends through the tubes a to the 
lower header c, from which it flows back to the bottom 
of the jacket. As the water cools in the tubes or, a, it 
descends; and as it becomes heated in the jackets d, d, it 
rises; thus causing a continuous circulation. As it is essen- 
tial that the return pipe be filled with water (else the dr- 




culation would at once stop), it is customary to make the 
top manifold b large, as illustrated, forming a small tank 

Fig. 25 

^^'^taining a couple of gallons or so of water that will take 
^^^irie time to evaporate. 

In any cooling system where the supply of water 
^^ limited, it is very essential that the movement of the 
^^ter shall be rapid, and this means that there will be a 

^fiference of only a few degrees between the temperature of 

^^ 'water entering and that leaving the radiator. With so 
^^^^11 a difference in temperature, and therefore in density, 

^^ impulse toward circulation in the gravity system is very 
^^^11, and it is of first importance that the pipe connections 
^^t.'Vreen the jacket and radiator shall be very large, short, 
^^^ devoid of sharp bends. In fact, it is not uncommon 

^ lase two or even three connections from the radiator to 
^^^ bottom of the jacket, in addition to making the upper 
^^"'inections as large as possible. 

In the majority of cars, gravity circulation is not 

^^l^ied on, either because it is not convenient to make the 

^^ter connections sufficiently short and direct, or because 

^*^^ motor rises too high in the frame or is of too high power 

^ "be cooled in this way without employing a radiator of 



undue size. Consequently, a circulating pump is usually 

A cooling system of this type is shown in Fig. 26, with 
the circulating pump located at a^ the radiator at /;, the 
engine water-jackets at r, c^ and the carbureter at d. The 
water circulates through the pipes in the direction indicated 
by the arrows. It will be noticed that the carbureter is 
surrounded by a water-jacket, through which a sm^ll 
amount of water is circulated to warm it, the water passing 
to the radiator, where it mixes with the other water as it 
goes to the pump. 


34, Types of Badiators. — Radiators are usually made of 
thin metal with as much surface exposed to the air as pos- 
sible, and they are arranged so that the air can circulate 
easily through them. Four forms of radiators are shown in 
Fig. 27 [a), (*), {c\ and {d). The first, Fig. 27 {a\ consists 
simply of a zigzag coil of copper tubing, on which are soldered 
a large number of thin flanges that increase the surface 
available for contact with the air. The one shown in 
Fig. 27 {V) is quite similar to that shown in Fig. 27 (^), but 
somewhat more complete, in that it has headers at the ends 
to which the flanged tubes are connected. The whole 
arrangement is enclosed in a sheet-metal casing having the 
outline of the automobile front. The one shown in 
Fig. 27 (c) consists essentially of top and bottom headers 
connected by a large number of thin flat tubes, crimped into 
zigzag shapes and placed vertically as close together as pos- 
sible. In this way the water is divided into a large number 
of thin sheets contained in passages between thin metal 
walls, through which the heat of the water passes rapidly to 
the air drawn through them by the speed of the vehicle, 
aided usually by a suction fan just behind the radiator. 
Circulation is generally maintained by a pump, and the 
water enters the top of the radiator from the water-jacket, 
and goes out from the bottom to the pump and thence to 
the bottom of the jacket. 


Fig. 27 {iff shows the back view of a type of radiator that : 
[ ctMisJsts of a shell with front and back tube plates into vrhidi 
I are connected a large number of small horizontal tubes. 

The water inside the radiator surrounds the tubes, and tjip J 
r that does the cooling passes through tliem. Tho £ 
\ aids in the circulation of the air. It is held in place \ 


three braces by c, and d. The water enters the radiator at 
the upper right-hand comer through the connection e, and 
leaves through the opening /at the lower left-hand comer. 

35* Bemoval of Scale From Radiators. — Owing to the 
narrowness of the water spaces in all forms of radiators, it is 
extremely desirable to keep them as free as possible from 
deposit and sediment of all sorts. On general principles, it is 
well to empty and wash the radiator occasionally, and in 
regions where the well and spring water is hard, rain water 
only should be used when it can be had. The use of hard 
water has the result, if the water gets hot, of precipitating 
in the jacket or radiator a scale exactly like that which forms 
in boilers. Even if the radiator is of the tubular type, 
this scale is objectionable because it interferes with the free 
transfer of heat from the water to the air. 

Carbonate of soda, or common washing soda, is used for 
the removal of scale from radiators. It breaks up the hard 
deposits of scale into a powder or sludge, which can easily be 
removed by subsequently flushing out the radiator and pip- 
ing thoroughly with water. 

The water in the circulating system is drawn off and 
measured, care being taken that none is left in the pockets 
to dilute the soda solution. The solution is made in the pro- 
portion of 2 pounds of soda crystals to 1 gallon of water. 
The circulating system is entirely filled with this solution, 
which is allowed to remain all night. After drawing it off 
in the morning, a hose is connected and a good stream 
of water driven through at the best obtainable water pres- 
sure for some time, or until the water comes off clear. 


36, Types of Clrcvilatlng Pumps. — Of the various 
types of circulating pumps, by far the most common, and in 
some respects the most efficient, is the centrifugal pump 
shown in Fig. 28. In this pump the only moving part is a 
bronze or aluminum disk ^, keyed on a shaft b, and on 




one face are cast blades c^ r, which may be radial, as shown, 
or bent backwards. The shaft carries the disk a at one end, 
and works through a stuffingbox to prevent leakage. The 
water enters from the opposite side of the pump through an 
opening indicated by the dotted circle d^ but which is on the 
side toward the observer, so that the water as it enters the 
pump meets the blades c. The water so entering is caught 
by the blades and thrown outwards by centrifugal force, 
being expelled at r. It is not necessary that either the disk 
or the blades have a water-tight fit in the casing, since the 

pump simply establishes a 
difference in pressure between 
the points d and ^, but does 
not positively force the water. 
Consequently, if the flow is 
obstructed for any reason, the 
pump can still be revolved 
without injury to itself. More- 
over, th's type of pump does 
not lose its efficiency through 
wear. The pump is run at 
quite a high speed, generally 
about twice the speed of the 
engpine ; and.if the resistance to 
circulation is not too great, it will throw quite a large stream 
of water. It is usually mounted on the crank-case of the 
engine and geared to the cam-shaft or to the two-to-one 

37. A type of pump used to some extent for circulating 
]nirposes on automobiles is shown in Fig. 29. It is called a 
^(^ar-punip, iind it operates equally well in either direction. 
( )ne of the two gear-shaped pump members a is driven bv 
a shaft, and it rotates the other with it. If the direction of 
rotation is that shown by the arrows, the water will enter at 
/;, and pass out at c. beine:" carried around by the outer teeth 
d, d, and c, i\ and expelled as the teeth come together. The 
particular pump shown has grooves/, f\n the sides and tips 

Fig. 28 


s teeth, which, it is claimed, prevent lo a large extent 
i past the teeth, and thereby increase considerably 
ciency of the pump. 

, ^^8. Another type of pump is shown in Pig, 30. It con- 
■^ts of a cylindrical barrel a revolving eccentrically in the 

chamber i. The shaft on which a turns is central with a, 
and the water is moved by the two blades c and (/, pressed 
iiHtwards by the spring r. The action of the pump depends 
on the motion of the blades c and 1/ in the chamber i^. Sup- 
itee barrel « to be in the position shown and rotating in 




the direction of the arrow until d has co^-ered the edge/ of 
the iataee port; the water in front of the blade d will Uien be 
driven before i/and out by the port/: Meanwhile, as sooi 
as d has covered /, water is drawn into the space h behind d 
until d has nearly reached the position of c. This operalicm 
is repeiited by the tn'o blades, thus producing an almost 
continuous flow of water. 

39. Circulation Pressnre Gange. — In order that the 
operator of an automobile may know whether or not the 
cooling water is ctrcnlatiiig 
properly, a pressure gauge 
such as is shown in Fig. 31 is 
placed in the piping circuit 
The gauge, which is frequently 
styled a telltale, is usually 
attached to the dash in such a 
position that it may readily be 
seen, the pressure created by 
the pump and registered by 
the gauge in ounces per square 
inch giving some idea as to the 
velocity with which the water 
^'^- " . is passing through the circu- 

lating system. If the gauge fails to register, it is evident 
that no water is flowing through the piping. 


40. Automobile and marine mufflers are generally very 
similar in construction, except that the marine types are 
often water-jacketed. Especially in automobile types, it is 
desirable that they be as light in weight a» they can be made 
and do the muffling properly, A muffler of this type, in 
which the gasesaro deflected by a scries of conical baffle plates, 
is shown in Fig. 32. The exhaust gases enter through the 
pipe a, flow into the central tube b, and a small portion passes 
out through the oi«ning in the nozzle c to the outlet pipe i. 



The velocity of the gas through the nozzle creates a partial 
'■■acuuin in the chamber c. The opening in the nozzle being 
soiaH, a portion of the exhaust gases flows around the end of 
the tube b to the chamber/. The partial vacuum me draws 
the fases through the baffle plates^, one being perforated 

'^^ar the center, and the next near the outside, so that the 
Sases move in the direction of the arrows. The body of the 
"muffler is composed of two steel cylinders, with asbestos 
packed bet\veen them, and closed at the ends by flanged heads. 
^liis muffler does not create an excessive back pressure on 
^oe engine, and reduces the noise considerably. 

41, Another type of muffler is shown in Fig. '.i'i. The 
ffases enter at a, pass to the opposite end through the pcrfora- 


^"■itis, and around the ends of the baffle plates b and through 
^ openings r Tbey then pass back outside the cylinder d. 


through the openings e in the cylinder f^ and finally o 
through the openings^. A relief valve // is held in placr 
against the openings i by a spring. When the back pressur' 
becomes excessive the valve opens, or it may be opened b 
a treadle near the driver, the treadle operating through a r 
attached to the lever / 

42. Two forms of mufflers for marine engines are knowr::^^^^^^-*' 
as the ivet and jacketed viufflers or the construction maj 
represent a combination of both of these types. In the 
Jacketed muffler, water from the cylinder water-jacket 
outlet is allowed to circulate around the outside of the muf- 
fler, to assist in cooling the gases and thereby reducinj 
their volume. The 'wet muffler is one in which all or 
|xirt of the exhaust water from the water-jacket is dis- 
charged into the engine exhaust, where it is turned int( 
steam, cix^s the exhaust gases, and combines with them, 
incre;ising their density and sluggishness, and thereby muf- 
fling the exhaust. The water from a jacketed muffler ma; 
Ik divortevl into the exhaust itself, to further reduce the 
souuvi of the exhaust, this being the combination systenc 
alx>vo montionoi!. 

Mut^ing a well-designed engine results in more orle 

Kick pressure in the exhaust, and as a result the product 
ot oxMuhusiion arv not so thoroughly removed from 
explvvsion chamber, with a resulting loss of efficiency. It -i s 
t\^r this reason that many marine engines are but slight"Xy 
wurtk\K the :nort>ai<xl noi^e not being quite so objectionat^l^ 
as it woulv! !x^ in an autv^mobile used in the streets. 



Types of l*wjpellers. — The screw propeller is a very I 
tanportant part o£ the power equipment of a launch orl 
"lotor boat. The rotary motion imparted to the crank-shaft-l 
^ the gas engine inside the boat is given to the propeller J 
outside the boat, and by its action on the water the boat i 
propelled forwards or backwards. Motor boats are sel'' 3m I 
T^m backwards for any 
ffneat distance, the back- 
Ward motion being prin- 
cipally used when get- 
ting away from a wharf 
*T dock, when stopping 
quickly, or when turning 
"^ a small space. The 
**oat always moves more 
rapidly forwards than 
"ackwards, with the same 
Expenditure of power, ' 

I^'igfi. 34 and 35 show 
two forms of propellers. 
^>gr. 34 has a very wide 
bla.tic near the end, while Fig. 35 has the greatest width at ! 
* point about one-third the distance from the end of the | 
olacJe. Propellers are also made with two and with four | 
'''acles; when made with two blades they are opposite, or J 
^^O" apart. The blades on a four-bladed propeller are J 
dually spaced around the hub. 

■As the propeller turns in the water, its motion is resisted 
"^ the water, and this resistance increases with the speed of 
'**^ propeller; besides, when a propeller turns very rapidly, 
't Chums the water without increasing the speed of the boat. 
"^^e speed limit of propellers seems to be reached in prac- 
tice at about 800 revolutions per minute ; it is probable that, 


at speeds in excess of 800 rKvolutions per minute, cvenn 
e in power at the engine is tnoie 
than CO unterb;t lanced 
.!'! neutralized by pro- 
"J llcr losses. In heavy, 
, ■■; working, boats, the 
] OSS of efficiency at high i 
■^pt-ed is verj- much 
;;ri;aler than in lighl 
boats. It has been ob- 
served that, in heavy 
head winds, working 
boats that make but 
little progress witl) the 
engine running at 3fi(l 
'^'^- " revolutions per minute 

will do considerably better at 20 per cent less speed. 

44. Pitch or PropeUer. — The pitch of the propeller 

is the axial, or longitudinal, distance through which the 
propeller would force the boat, in one revolution, if there 
were no resistance. The amount the resistance reduces the 
longitudinal motion of a boat is called the slip. The pitch 
of a propeller is measured in the same way that the pitch of 
a screw is measured. If a screw has eight threads in I indi 
of length, the distance from one thread to the next is \ inch 
and the pitch is consequently \ inch; that is, in moving a 
point around the screw thread once, it advances \ inch along 
the axis. In the three-blade propellers shown in Figs. W 
and 35, it will be noticed that there are three distinct sur- 
faces, all of which have the same pitch, and that these 
surfaces resemble a portion of ascrew with three threads. 

The diameter of a propeller is the diameter of a circle 
described by the tip of the longest blade. If the circumfBT- 
ence of the circle of any point on a blade is laid off on a 
straight line, the pitch laid ofEat right angles at one end, and 
the triangle completed, it will form a right triangle, as shown 
in Fig. 36. Let the base a b represent the circumfer 


of a circle described by a point on the tip of one of the 
blades of a propeller; b r, the pitch or distance advanced 
along the axis in one revolution ; and a c^ the line complet- 
ing- the triangle. The line a c then represents the direction 

PlO. 86 

of the face of the propeller blade, and the angle bac\^ called 
the angle of advance. The circumference for a point one- 
half the distance from the center of the axis to the tip of 
the blade is one -half as long as the circumference for the 
point at the tip. Let the point d be located, on Fig. 36, mid- 
way between a and b\ then, if the pitch is the same, the angle 
of advance b d c \s greater than the angle of advance^ a c. 

4:5, A propeller with the same pitch for all points of the 
blade is said to have unifonn, or true, pitch. A pro- 
peller blade has increasing:, or expanding:, pitch when 
the pitch increases from the axis to the tip of the blades, 
and decreasing pitcli when the pitch at the axis is great- 
est and it decreases toward the tip of the blade. Com- 
poand pitch is any combination of pitches. The propeller 
might have true pitch at some parts, and increasing or 
decreasing pitch or both at other parts. 

Fig. 37 shows, diagrammatically, the difference in the angle 
of advance for different points of blades having true, increas- 
ing, and decreasing pitches. Let the length of the line a b 
represent the circular distance traveled by the tip of the 
blade in one revolution, and let b c represent the pitch of 
the blade at the tip. Let the points d^ t\ and f be at 
three-quarters, one-half, and one-quarter the distance 
a b from b and on the same blade. Then, for true pitch 
the length b c \^ the pitch for all these points, and 
the lines drawn from c to /", ^, d^ and a make decreasing 


angles with the line a b, that is, for a propeller of nnifonn 
pitch, the angle of advance decreases from the axis toward the 
tips of the blades. If, on the other hand, lines are drawn fTom 
d, e, and / parallel to a c, as d g, e h, and ft, making the same 
angle with a b — that is, if all points of the propeller blade 
have the same angle of advance — the pitch increases from the 

axis to the tips of the blades. The pitch at one-quarter the 
distance from the axis to the tip is b i; at one-half it is b h, at 
three-quarters it is bg; and at the tip, it is i c. Propeller blades 
having such angles would be said to have increasing pitch. 

Continue the line b c beyond c, and lay off the points/, k, 
and /, and draw the lines dj, e k, axiA/l. When these lines 
represent the angles of the faces of the blades at different 
points, the pitch from the point / where it is b /, decreases 
toward the tip, where it is b c. Conse'qnently, such a pro- 
peller would be said to have decreasing pitch. 

46. Measuring Plteh of Propeller. — In practice, the 

pitch of a propeller may be found quite closely in the man- 
ner illustrated in Fig. 38. Take a piece of joist or lath />. 
which should be as straight as possible, and place it so that 




it touches one of the blades at any distance, as d, from the 
axis A By taking care to hold it parallel with the axis. 
Next take a carpenter's square, shown at £, and place it on 
the lath and against the blade, so that the point at which 
the square touches the blade will be the same distance from 

Fig. 88 

the axis as is the lath. Measure the distances a, b^ and c — 

a being the distance from the square to the point at which 

the lath touches the blade, and c the distance from the point 

at which the square touches the blade to the lath. Then 

the distance c is to the distance a as the circumference at this 

point is to the pitch. Expressed as a formula, the pitch is, 


^ c 

where/ = pitch of blade; 

a = measurement taken along axis; 
c = measurement at right angles to a 
b = radius where pitch is taken. 

ExAMPLK.— If the distance a is 10 inches, b 12f inches, and c 20 inches 
what is the pitch ? 

Solution. — Apply in j2f the formula, 

6 2882Xl0Xl2.fi25 

i> = 


- = 39.66 in., or, sav. 40 in. Ans 


^B 47. It nfLen Ikcoihis necessary tu measure the pil 
^M a propeller accurately, and the only manner in which it c 
^H doneisbydran'ingtwciprofilesof one of the blades. gOi 




— ^J 


fc.-.-. '^ 

Fin. at ^H 
|^«j|kf, -"^■■"' - -rMeron astcelmanarel^B 
^^H| : ■■■.-asary tncasuremenix. ^| 
^^^ftl o-'tcr, and long oaaugh^^l 




through the wheel, with a round shoulder at ^ 2 inches in 
diameter, and an extension c )-inch in diameter and \ inch 
long. Two roimd hardwood tapered bushings d and e should 
fit the two ends of the hole in the propeller, and the mandrel 
inserted so that the wheel shall retolve at right angles to 
the mandrel. It may be necessary to add washers at/to 

allow the front or cutting edge of the wheel to be above the 
lower surface of the shoulder b. The mandrel should then 
be set into a drawing board g, on which are circles con- 
centric with the mandrel, as shown. A line a b can be 
drawn as shown on Fig. 40, the axis laid off at c d, 
and lines drawn parallel to c d and spaced the same dis- 
tance apart as the circles in 
Fig. 30. Then, by taking 
a square, as shown at //, 
the height of the lower side 
of a blade can be measured 
as shown at t, and this dis- 
tance laid off on the corre- 
^"'"^' sponding line, as shown at 

i in Fig, 40, Then the square can be set on the other side of 
the blade on the Sfiine circle, the highest point measured as 
at/ Fig. 3i), and laid off as shown at J in Fig. 40. If the 
angle of the square is set carefully on the circle, the point 
where it touches the circle marked, and the process repeated 
on both sides of the blade for eacli circle, a line can be 
drawn through these points, giving the end view as shown in 


Fig. 41, in which twelve measurements are taken. Having 
done this, the pitch can be calculated along any of the 
twelve circles by the formula in Art 46, taking the lengths 
of the arcs in Fig. 41 to represent c of the formula, the 
lengths of the corresponding straight lines in Fig. 40 to 
represent a^ and the distances of the circles from the center 
to represent b. 

When it is desirable to get increased blade area without 
increasing the width of the blades and making them corre- 
spondingly stronger, it is customary to use three or four 

The heavier the boat and the slower the engine speed, the 
greater the blade surface should be; while the lighter the 
boat and the higher the engine speed, the less the blade 
surface required, other conditions being the same. 

48. Propeller Blades. — The drlvingr snrfoce of a pro- 
peller is usually the flat side of the blade that pushes the 
water astern, while the crownings surftice, or firont, is the 
part that draws the water toward the propeller. 

The cutting edge is the part of the propeller blade that 
first enters the water when driving the boat ahead. 

The projected area of the blades is the surface that forces 
the water back, and is measured at right angles to the direc- 
tion of motion of the water. Fig. 40 shows a profile of a 
propeller blade taken at right angles to the shaft, while Fig. 
41 shows a profile in the direction of the shaft. The area of 
Fig. 41 multiplied by the number of blades would be the pro- 
jected ai*ea of the propeller surface, while the developed 
area would be the entire driving surface of the blades, usu- 
ally called the blade surface. 

The accepted form of blade surface to give the best results 
is what is known as a warped surface. In someone direc- 
tion on such a surface, straight lines can be drawn, but to the 
eye, and by the application of a straightedge in any other 
direction, it has a slightly dished or concave surface. 

49. Slip of Propeller. — The apparent slip of a pro- 
peller is the difference between the actual speed of the boat 




with reference to some fixed point on shore and the 
speed at which the propeller would cut ahead, or travel 
through the water, without resistance or slip. 

The apparent slip, often called simply the slip^ is gener- 
ally used in determining the action of the propeller. To 
test a propeller on a boat, in order to determine its apparent 
slip, its action should be observed when running the boat over 
a measured course. This ^ay be done before or after the 
pitch of the propeller is measured. The number of revolu- 
tions of the engine should be recorded carefully, with the 
length of time to cover the course. The boat should be 
driven at a maximum speed, and if there is a known current 
its velocity should be added when running against the curr 
rent and subtracted when running with the current The 
engine should then be slowed a little, and the revolutions 
and time again recorded. These results should be figured 
out carefully and tabulated somewhat as follows: 

Course If Miles, or 7,260 Feet, Pitch of Propeller, 

40 Inches 

tions Per 



Actual Speed 

Per Hour 


Speed Per Hour 
with No Slip 



. Sec. 




9- 556 


























The speed per hour can be computed by using the formula 


;r = 60 



in which a = time, in minutes, elapsed in traveling over the 

b = length of course, in miles; 
X = rate of speed, in miles per hour. 


Thus, at 180 revolutions per minute, the speed in t 
table, taking 13f minutes as the time to travel If mil< 

would be ;r = 60 X zrA- = 6.037 miles per hour. KnowioK — S 


the pitch of the propeller, and the number of revolutio 

per minute, the speed with no slip can be calculated by 


in which s = speed with no slip, in miles per hour; 
n = number of revolutions per minute; 
/ = pitch of propeller, in inches. 

Example. — If the pitch of a propeller is 40 inches, and the number 
revolutions per minute is 180, what is the speed with no slip? 

Solution. — Applying formula 2: 

180 X40 ^Q,Q . , . 

s = ^ vl^ =6.818 mi. per hr. Ans. 

The difference between the cutting ahead and the actu -^^■-^ 
speed is the slip, which in the example just given ^ ^ 
0. 818 — 6. 037 = . 781 mile, the rate of slip being the percenta^ 
.781 is of 6.818, which is 11.45 per cent The table shoi 
that the slip increases with the speed of the engin< 
natural result. 


60. Increasing the blade surface of a propeller, leaviscrB-.^ 

the pitch and diameter the same, will reduce the eflfectL^^^^^ 
power of the engine and the percentage of slip; whi^^ 
decreasing the blade surface will increase the effective po^^^^^ 
by reducing the resistance, the slip being increased. Incre^a*-^" 
ing the pitch or reducing the diameter of the propeller sm^^^^ 
increase the percentage of slip, but will also increase tl^e 
effective power of the engine ; while reducing the pitch <^^ 
increasing the diameter of the propeller will reduce tb^ 
percentage of slip and decrease the effective power c>i 
the engine. 

Whether the speed of the boat will be helped by decrease 
ing the blade surface and increasing the pitch, or vice ver*^ 


can be determined only by trial, there being so many com- 
binations of conditions that the best designers of propellers 
frequently fail to obtain satisfactory results. By mak- 
ing an analysis of the propeller, pitch, blade surface, etc., 
and studying the results of tests, it is frequently possible to 
improve the speed of the boat by change of propellers, but 
such a change should not be made by guess. Propeller 
experiments are quite likely to be expensive. 

When the pitch of a propeller is increasing or decreasing 
it is difficult to measure, and it is customary in that case to 
measure the pitch at a point one-third of the distance from 
the end of the blade to the center of the shaft, and the pitch 
thus measured is usually referred to as the mean pitch. 
Or, the pitch may be measured at several equidistant points 
each side of the center of the blade, and a mean of the meas- 
urements taken as the mean pitch. 

61« Beverslng Propellers. — In some cases it is found 
expedient to use reversing or feathering blade propellers. 
The blades may be feathered or the angle at which the driv- 
ing surface strikes the water may be so changed that the 
water is driven ahead instead of astern, without reversing • 
the direction of rotation of the propeller shaft. Midway 
between the ahead and the astern posi tion is a neutral zone 
in which an equal power in both directions is exerted, with 
no effect on the boat in either direction. There is usually 
but one position of the blades that approximates true pitch, 
and on this account there is a considerable amount of power 
lost in their use, unless they are very carefully designed and 
specially built. 

A sleeve sliding on the shaft and connected to the blades 
themselves, often within an enlarged hub, or attached to it 
and operated by means of a lever or hand wheel inside the 
hull, is sometimes used to control the position of the blades. 
Such an arrangement is shown in Fig. 42 {a). The propeller 
blades are shown at a, a, the outside stuffingbox at b, the 
stem bearing at r, the sliding sleeve at ^/, the inside stuffing- 
box at ey and the reversing lever at /. One of the blades 




separate from the device is shown in Fig. 42 (^), with the 
pivot g that fits into the hub and about which the blade tumsi 
The pin h of this blade fits into the slot i in the fork y* Fig. 
42 (a) and {c\ The fork is attached to the sleeve d^ and as 

PlO. 42 

the sleeve is moved forwards or backwards the fork moves 
the pins so as to cause both blades to turn about their 
pivots. The propeller shaft is shown at k. The sliding 
sleeve revolves with the shaft, but is free to be moved along 
the shaft by the lever/. 




1, It is sometimes desirable or necessary to operate a gas 
engine independently of a central gas plant. In such cases, it 
is possible to produce the fuel gas required to run the gas 
engine at a lower cost than when using either illuminating gas 
or the more volatile grades of liquid fuel, such as gasoline 
and distillate of petroleum. This has led to the gradual 
development of an apparatus known as a pcwer-gas 
producer, which is practically a small gas plant located 
near the engine, to which it furnishes gas. The process of 
making gas from coal, coke, or charcoal by means of such a 
producer is a simple one. The gas-generating and purifying 
devices are of such size as to be readily installed in power 
plants using gas engines and operating under ordinary 
conditions. They occupy but a small amount of space, and 
the attendance, even in a fairly large plant, requires only a 
portion of the time of one man. 

S* Classification of Producers. — Modem gas produ- 
cers may be divided into two general classes namely, 
pressure producers and suction producers. 

In pressure producers, the gas is generatea oy forcing 
a blast oi steam from a boiler, or of moistened air from a 
blower, through a bed of incandescent fuel. The gas is puri- 
fied in a scrubber, stored in a gas holder of suitable capacity, 

C^pyrigktedby International Textbook Company. Entered at Stationer* s Hally London. 



and supplied to the engine at a pressure of from 2 to 3 
ounces. Pressure producers are generally used in large 
power plants and where more than one engine is supplied 
from the producer. They are also adapted to the use of dif- 
ferent kinds of fuel. 

In suction producers, air and water vapor at atmospheric 
pressure are drawn through the incandescent fuel by the inhal- 
ing or suction action of the engine, due to the partial vacuum 
produced in the engine cylinder during the suction stroke of 
the piston. The gas so generated is cooled and purified in 
the same manner as in the pressure producer. The volume 
of ga? in a suction producer is thus never in excess of that 
required by the engine, and consequently it is not necessary 
to provide a holder, the gas being drawn directly from the 
producer to the engine cylinder. The amount of gas genera- 
ted depends on the force of the suction or the number of 
inhalations transmitted from the engine cylinder to the pro- 
ducer. The engine governor controls either the volume of 
the charges .or the number of charges required to operate 
the engine under any load. 

3, Power Gas. — The pressure process of manufacturing 
producer gas for power purposes has not been materially 
changed since its introduction 20 years ago by Dowson, in 
England. Producer gas had previously been used for heating 
purposes, in which case it was desirable to keep the tempera- 
ture of the gas as high as possible before being burned. In 
generating power gas the conditions and requirements are 
materially different, the desired object being the transforma- 
tion of the heat in the coal into the chemical energy of cold 
gas, because it is only in a thoroughly cooled condition that 
gas can be used efficiently in engines. 

In the pressure process of generating gas for heating pur- 
poses, the dry air is heated before being introduced into the 
producer ; in the generation of power gas, on the other hand, 
the object is to reduce the temperature of the gas as much as 
possible by admitting to the producer a certain amount of air 
and water vapor, so that, when the mixture is brought in 


contact with the burning fuel, hydrogen will be liberat^r<i. 
With even this cooling effect, however, the gases leave 
producer at a temperature that is generally above 900° F. 

The process of manufacturing power gas consists prin 
pally in heating some form of fuel to a very high tempe 
ture in a vessel from which the atmosphere can be excluded. 
The vessel in which the heating takes place is called the 
producer, or grenerator. The vessel in which water is 
heated, in order to supply moisture to the air that is admitted 
to the producer, is called the evaporator, or boiler. 

After the gas is made in the producer, it is purified and 
used directly, or else stored in suitable tanks. The several 
steps in the process of gas generation will be treated in detail 
in connection with the various types of producers. 


4, One of the first types of pressure producers, as intro- 
duced by Dowson in England, and of which several plants 
have been installed in America, is illustrated in Fig. 1. Tb^ 
boiler a generates steam at from 60 to 75 pounds pressure, 
the steam being conveyed to the injector b through the pipe ^- 
In the injector, the steam is discharged through a small no^* 
zle, and the issuing current draws with it a certain amoun* 
of air from the casing d surrounding the pipe r, through 
which the hot gases leave the producer /i Thus the injector 
serves merely to deliver a mingled stream of air and steam 
to the ash-pit ^ of the producer, beneath the grate. 

The producer consists of a cylindrical shell made of steel 
plates and lined with a highly refractory grade .of firebrick. 
A hopper //, which is closed toward the atmosphere by 4 
removable lid /, and against the interior of the producer bf 
means of the bell j\ conducts fuel to the producer while in 
o|XTation. The bell being tight against its seat, the lid can 
be removed and the hopper filled with fuel. After closing 
the hopper, the bell is allowed to drop, permitting the fuel to 
enter the firepot of the producer, where it descends to the 


e and is constuned, the ashes and clinkers beingf removed 
ugh the door k. 

• The steam entering the producer is decomposed into 
fen and hydrogen while passing through the incandes- 

fueL This oxygen, together with that which is in the 
mixed with the steam, unites with the carbon of the 

to form carbon dioxide and carbon monoxide. These 
IS mix with those produced from the fuel by the 
: and pass upwards through the port / and the 

I e. The pipe e is provided with fittings having remov- 
handhole covers, for the purpose of giving easy access 

ase it becomes necessary to clean the pipe. The gas is 
t forced through the water box w, where it is washed and 
t of the impurities removed ; it then enters the scrub- 
«, which is filled with coke to within a few inches of the 
et pipe o near the top. As the gas rises in the scrubber, 
met by a descending shower of water distributed over 
entire area by me^ns of the sprinkler/. The water cools 
gas and carries away some of the impurities, leaving a 

II portion deposited on the coke. The coke is placed in 
scrubber with the larger pieces at the bottom, the sizes 
lually diminishing toward the top, and need not be 
5wed for a period of from 1 to 2 years, according to 

quality of the fuel used in the producer and the 
►unt of tarry matter contained in the fueL After the 
5 becomes clogged, the scrubber is emptied and fresh 
5 provided. 

ny dust or other impurities that the gas may contain 
r leaving the scrubber is removed while passing through 

purifier box q — ^sometimes called a sawdust purifier — 
ch consists of a square box with a removable top and con- 
s a series of wooden gratings r, over which are spread 
rs of sawdust or similar material. The gas is now ready 
>e stored in a holder, not shown in the illustration, from 
A it is supplied to the engine in the same way as illumi- 
ng gas> t>ut of course in larger quantity, proportionate to 
Dwer heating or calorific power. 


6, The gas generated when the producer is first starti 
is of very poor quality and unfit to be stored in the hold< 
It is therefore permitted to escape into the atmosphe 
through the smoke and waste-gas pipe j, until, by a test ma« 
at the tube /, the gas shows that it is of the proper quality, 
burning with a bright blue flame. As soon as the quality 1»^ ^ 
come up to the desired standard, the valve u in the wa^t 
pipe is closed, and the gas is allowed to pass on its vr ^ 
through the scrubber to the holder. The overflow from L^la 
water box m passes through the water seal v^ which pena-il 
the water to flow to the sewer without allowing any gas t 

It will be seen, by an examination of Fig. 1, that all pii:>ej 
between the producer and the holder are provided with fit- 
tings having handholes and covers, so that the pipes can 
easily be cleaned as occasion may require. It must be under- 
stood that, especially when using the poorer grades of coal, 
some of the impurities contained in the gas will adhere to 
the walls of the pipes, and in time sufficient quantities may 
accumulate to interfere with the free flow of the gas from 
the producer to the engine. 

The pressure of the gas at the point where the injector b 
connects to the ash-pit of the producer is about 8 inches of 
water. This pressure gradually diminishes on account of the 
resistance that the gas encounters during its passage from 
the producer to the holder. Measured by a water gauge, the 
pressure in the pipe e between the producer and the water 
box is equal to about 6 inches; after leaving the scrubber, 
the pressure is 4 inches, and before entering the holder it is 
2 inches. 


7* Comparison of Suction and Pressure Producers. 

A comparison of the pressure producer with the suction produ- 
cer discloses the fact that the chemical changes brought about 
in both types are practically the same. The difference between 
the two types is therefore not in the nature of the product 


but in the manner in which the gas is transmitted from the 
gas apparatus to the engine. The processes of generating 
and purifying the gas are the same in both cases; but in 
the pressure producer a pressure above that of the atmos- 
phere is maintained by a forced draft, either from a low- 
pressure steam boiler or from a blower; while in the suction 
producer the pressure in any part of the apparatus or its 
connections is never higher than that of the atmosphere. The 
draft in the suction producer is furnished by the engine pis- 
tori during the suction stroke while the inlet valves are open, 
and the vacuum created in the cylinder causes the gas from 
all parts of the producer apparatus to flow toward the 

The difference in pressure between the two systems is 
practically 8 inches of water; so that, in the suction pro- 
ducer, the pressure of the gas as it leaves the scrubber is 
about 6 inches of water below atmospheric pressure instead 
of 2 inches above, as in the case of the pressure producer. 
The relative difference in pressure in the various parts of 
the apparatus is the same in both systems, and the order of 
the operations of the process is necessarily alike in both 
cases. The suction type of producer does not require a 
large gas holder, a small cast-iron or sheet-metal tank being 
used instead. This tank is but slightly larger than the cus- 
tomary gas bag or pressure regulator used in connection 
with engines using illuminating gas. 

8. Supply of Air and Moisture. — ^A suction gas pro- 
ducer of small capacity, in which the evaporator for supply- 
ing the necessary moisture to the air is mounted directly 
above the producer shell, is shown in Fig. 2. The apparatus 
consists of the producer a with a cast-iron shell; the hand- 
operated blower ^, for reviving the fire, after a shut-down 
over night; the evaporator c\ the hopper d\ the water 
trap e\ the water-seal box f\ the scrubber g\ and the gas 
tank or reservoir h. At each suction stroke of the engine, 
air is drawn into the top of the evaporator c^ through the 
elbow /, which is open to the atmosphere. The evaporator 


is filled with water from a branch pipe taken from the main 
supply pipe and kept at a constant level by an overflow 
pipe, not shown in the illustration, that carries any surplus 
supply to the ash-pit j. The water in the evaporator is 
heated to about 170° F. by radiation from the burning fuel 
and by the hot gases that leave the producer through the 

The air passing over the surface of the hot water absorbs 
a quantity of vapor, the amount depending on the tempera- 
ture of the water; so that the quantity of the water vapor 
admitted with the air through the pipe / to the space below 
the grate is greater when the fire is hot than when it is low. 
The fire is hottest, of course, when the engine is carrying a 
heavy load. Under heavy load, not only does the increase 
in the amount of vapor enrich the quality of the gas gen- 
crated, but also the moistened air has a correspondingly 
S^reater cooling effect on the grate and tends to keep the fire 
at a proper degree of intensity. 

9. After entering the ash-pit below the grate, the mix- 
ture of air and steam is drawn upwards through the hot bed 
0^ fuel, where the steam is decomiposed into hydrogen and 
oxygen, and the formation of carbon monoxide takes place. 
After transferring a portion of its heat' to the water in the 
evaporator, the gas leaves the producer through the port ky 
passes through the water trap e^ and enters the scrubber at 
the bottom. The water trap has two pipe connections to 
the water-seal box/, the lower pipe being provided with a 
valve m. While the plant is in operation, this valve is open 
^d the water that accumulates in the bottom of the scrub- 
her flows through the lower connection to the seal box /and 
thence through an overflow funnel n to the sewer. When 
the plant is shut down, the valve ;// should be closed, thus 
fusing the water in the trap e to rise well above the lower 
®n<J of the partition wall o. This closes the gas connection 
'^tween the producer and the engine. Any excess of water 
^^n flowing to the seal box passes through the upper pipe 
attached to the trap e and thence to the sewer. 


1(). Passajuro of Giis Throug:li Scrubber. — While the 
gas is rising" through the coarse coke in the scrubber gy it is 
met by a descending stream of cold water which is distrib- 
uted evenly over the area of the scrubber by means of the 
sprinkler / attached to the top cover-plate. In this man- 
ner, the gas, from which some of its impurities have been 
removed while passing through the trap t\ is now cooled and 
washed sufficiently to be delivered to the gas tank // in such 
condition that it contains no tarry or dusty substances to 
interfere with the successful running of the engine. When 
semianthracite or similar fuels containing higher percent- 
ages of tarry matter than pure anthracite or charcoal are 
used, it is necessary to add a sawdust purifier similar to that 
used in connection with the pressure producer shown in 
Fig. 1. 

!!• Supplying: tlie Fuel. — The fuel is supplied to the 
producer shown in Fig. 2 through the charging device 
mounted above the hopper rf", which consists of the funnel q 
and a smooth hollow ball r that can be turned on its ground 
seat by the hand lever s. The ball has an opening at the 
top, so that it may be fill^ with coal through the funnel, 
after which it is turned over by a quick movement of the 
hand lever, bringing the opening in the ball in communica- 
tion with the coal space in the hopper d. As soon as the 
ball has thus been emptied of its contents, it is turned back 
and the operations of filling and emptying are repeated until 
the hopper is filled to the desired height. When not in use 
for filling the producer, the ball is held tightly on its seat 
with screws and hand nuts. The quick turning of the ball 
leaves but a small fraction of a second during which the 
hopper is open to the atmosphere, and practically no air is 
admitted to the producer at that point. 

12. Heiuovinjo: Aslies and Clinkers. — The removal of 

clinkers that form in the fire space of the producer is facih- 
tatcd by poke holes, with which the hopper is provided, that 
permit the fire to be stirred from above with suitable poking 


rodts. The clinkers descend to the grate and are removed 
through the two fire-doors /, /, on opposite sides of the cast- 
iron shell of the producer, while the ashes accumulating in 
th^ pit below the grate are drawn out through the ash- 
dooT //. 

A3. Starting: tlie Producer. — The hand-operated 
bloi^-er b serves to supply the blast necessary to start up the 
fire after the plant has been shut down for any length of 
time, say over night. During such a temporar}' shut-down, 
the process of gas making is practically stopped, except for 
the small amount of gas generated by the natural draft 
caused by the flue pipe v being kept open to the atmosphere 
^y opening the flue valve w. While reviving the fire, the 
valve «/, as well as the valve x in the vent pipe j/, is kept 
openuntil the gas escaping at the test tubes z^ z — one of which 
is placed in the pipes between the producer and the scrub- 
ber, and the other near the inlet to the engine— is of such 
quality as to bum with a bright blue flame. As soon as 
this is the case, the valve te/, and the valves in z and z are 
closed and the engine is started in the usual manner. To 
secure prompt starting, it is found advisable to keep the 
valve in the vent pipe y open to the atmosphere until a few 
explosions have taken place in the engine cylinder, and then 
close it. 


14. A suction producer of larger capacity than the one 
shown in Fig. 2 and Equipped with a separate evaporator is 
shown in Fig. 3. Instead of the castriron body shown in 
^^%' 2 in connection with the smaller type, the producer a 
consists of a shell built of steel plate and lined with fire- 
brick; but the hopper d and the coal-feeding device r are 
made of cast iron, and are essentially of the same construc- 
tion as in the smaller producer. Instead of a hand blower, 
a belt-driven pressure blower b furnishes the draft for 



The essential difference between the larger and the 
smaller plant is that the evaporator for heating the water in 
the smaller plant forms a part of the generator, while in the 
large plant it is a separate piece of apparatus and is con- 
nected to the generator by pipes. In the case of the larger, 
the evaporator consists of a cylindrical casting c with a hood e 
having a vertical dividing wall in the center, so that the air 
entering through the pipe /will be forced over the surface 
of the hot water in the evaporator before it passes to the 
ash-pit of the producer through the pipe g. Between the 
evaporator cylinder c and the hood is clamped a plate // car- 
rying a number of vertical tubes / that are kept full of 
water, the level of the water being kept constant by an over- 
flow pipey slightly above the upper surface of the plate //. 
The hot gases leave the producer through the pipe k^ and 
pass downwards and then upwards in the evaporator, being 
guided by the vertical partition /, and finally pass on to the 
scrubber m. In this manner, the water in the tubes is kept 
at the desired temperature, so that the required amount of 
vapor is taken up by the air while passing through the 
hood e to the ash-pit of the producer. 

In order to be able to control the amount of moist and dry 
air used, a regulating plate n is provided in the air pipe, by 
means of which the air-supply pipe can be opened to any 
desired extent to the atmosphere in the producer room, thus 
admitting cool air that has not come in contact with the hot 
water. The three-way valve o serves to shut off the air 
connection to the evaporator when the fire is being revived 
by the blast from the blower. As soon as the gas has 
become of good quality, the blower is stopped and the 
three-way valve set so as to admit air in the regular way 
through the pipe g. 


Iff, Another suction gas producer of somewhat different 
design is shown in Fig. 4. The producer itself consists of a 
l^liiftdricsl steel shell lined with firebrick and fitted with a 

enter the producer. Frotn tbe Isiipper, ihe fori i 

iolo the fiiv-»pi»c« thioQi^h the feeding tobe ^ sumnrndcd I 

the c\-»pot»tvir A in which the necessary steam i* generat ed 


at atmospheric pressure by the heat of the fire and of the 
gases when leaving the producer. 

16. The ashes are removed from the ash-pit g through 
the door h. A series of poke holes i distributed over the 
top of the producer permits rods to be inserted for the pur- 

pose of poking the fire and removing clinkers from the walls 
of the lining. Dry air is admitted to the ash-pit through 
the supply pipe /, while moist air, which is saturated with 
steam from the evaporator, is supplied to the ash-pit through 
pipes k, air boxes /, and nipples in. TJie air enters the top 
of the evaporator through the valve n. The proportionate 


amonnts of dry and moist air can be regulated as desired by 
opening or closing the valves n and o. The band-operated 
blower / is used for starting or reviving the fire. Kand- 
holes q in the top of the evaporator are provided for the 
purpose of removing any sediment that may accumulate in 
the bottom of the evaporator. The water supply to the 
evaporator is automatically regulated by the float r that con- 
trols a valve in the water box s. The water rising in the 
box raises the float and closes the valve, while the lowering 
of the float opens the water valve. The gas passes from the 
producer to the scrubber through the pipe /, which is con- 
nected to the top of the producer. 

17, An outside view of a producer of this type, con- 
nected to its scrubber, is shown in Fig. 5. The producer is 
shown at a and the scrubber at b. The hopper c with the 
filling device d is located aver the producer and is readily 
accessible by the stairs and the platform around the top of 
the producer. The fittings ^, ^', admit the air to the evap- 
orator, and the handles /are connected to the covers of the 
openings through which the fire is poked. The handle^ is 
provided for the purpose of rocking the grate, and the door 
h gives access to the fire. The vent pipe is shown at i and 
the main gas pipe at/, connected to the scrubber at ky with 
the water trap / extending below the scrubber. There are 
a number of manholes m, /«, on the side of the scrubber, 
to permit easy access to the interior. The water connections 
are shown at ;/, and the gas outlet from the scrubber at o. 
Producer plants of this style are made in units of from 15 to 
250 horsepower, and are very compact and convenient. 


18. A gas-producer plant in which the draft is furnished 
by an exhaust fan operated by a small motor, drawing the 
<^as from one scrubber and forcing it through another into a 
gasholder, is shown in Fig. G. This apparatus consists of two 
similar generators a and b, an evaporator r, a wet scrubber^ 


axhaust fan ^, a dry scrubber /, and the gas holder g. The 
► generators are of the doivn-draft type^ which is consid- 
^ especially adapted to the use of fuels containing tarry 
tter, such as bituminous coal, wood, etc. The gas and 
substances produced by the fresh fuel in the upper 
ion of the producer, pass down through the incandes- 
t fuel bed, where they are heated to a very high tempera- 
^^^^e, and a gas free from tar is thus formed. 

"ZIQ, The generators consist of cylindrical steel shells 
^^^ed with firebrick and provided with firebrick arches h that 
^^'pport the fuel beds. Openings i, /', at the tops of the gen- 
^"^ators, serve for charging fuel, and for the admission of 
^T, and the usual fire and ash doors are provided for clean- 
^"Jig the arches and for the removal of ashes. Steam jets/, /', 
One in each generator, are supplied from the boiler c. The 
toiler is of the vertical type, and is connected by brick-lined 
flues ife, k\ to the bottoms of the generators, the passages 
being controlled by water-cooled valves ///, m\ The hot 
gases leave the generators at the bottom, pass through the 
evaporator, and impart a portion of their heat to the water 
contained in the space around the tubes. The steam pro- 
duced is directed into the top of the fire by the jets/*,/. 
The hot gases pass up through the tubes to the outlet pipe. 

20« The wet scrubber «/, consisting of a cylindrical steel 
shell, contains a number of trays filled with coke moistened 
by the water sprays n and o, A purifier p filled with excelsior 
is attached to the top of the scrubber. The gas- inlet pipe / 
at the bottom of the scrubber is attached to a horizontal per- 
forated diaphragm q submerged in water, so that the gas 
must pass through the water before rising in the scrubber. 

21. The fan or exhauster c maintains the necessary vac- 
uum required to furnish the proper amount of draft and give 
sufficient pressure to deliver the gas to the holder. The 
motor that drives the exhauster is connected to the gas 
holder in such a way that the speed is automatically 


regulated, by the movement of the holder, to conform to the 
demand for gas. When the holder is full, the speed of the 
exhauster is decreased ; while in descending, as the gas is 
consumed, the motor speed is increased, creating a corre- 
spondingly stronger draft and a greater production of gas. 
The direction in which the gas flows after being delivered by 
the exhauster is controlled by the valves r and s. The valve 
r is connected to the waste-gas pipe and is kept open to the 
atmosphere while the fire is being started or revived. As 
soon as the gas becomes of the proper quality, the valve r is 
closed and the valve s opened, so that the gas can pass to the 
dry scrubber f and holder g, 

32. The dry scrubber contains two trays /, /', filled with 
excelsior, sawdust, or shavings. A horizontal partition u 
divides the scrubber into an upper and a lower chamber. 
The pipe connections to these chambers are fitted with 
valves, so that either the upper or the lower chamber can be 
connected to or shut off from the gas supply, thus making it 
easy to remove the trays, for the purpose of cleaning and 
recharging, without interrupting the operation of the appa- 
ratus. From the dry scrubber, the gas passes to the gas 
holder g, which consists of a stationary water tank t% filled 
with water, and an inverted movable tank it', which fits 
inside the water tank. The gas enters the holder through 
the pipe x^ whose upper end is slightly above the level of 
the water in the tank v. 

As the amount of gas in the holder increases, the movable 
tank iu rises, giving additional space for the gas between 
the water surface and the top of the tank iv. When the vol- 
ume of gas in the holder decreases, the tank %v descends. 
The pressure of the gas in the holder is thus kept constant. 
The lower edi^e of the tank iv is always submerged, forming 
a water seal that effectually prevents the escape of gas, 

23. While the a]^paratus is in operation, the generators 
a and b are open at the top, so that the attendant can observe 
the condition of the fire and add fresh fuel where needed. 


le condition of the fire may be regulated by occasionally 
ssing a jet of steam up through one and down through 
3 other generator, by means of auxiliary pipes ^jj^', cou- 
nted to the bottoms of the generators. The steam is 
roduced alternately in each generator; and the top door i 
1 the valve m of one generator are closed and steam is 
>\vn into the ash-pit through the pipe j^. This operation 
ises an up draft through one generator and a down draft 
•ough the other. 

Should wood be used as fuel, the generators are filled 
th coke to a height of 3 or 4 feet above the arches //, 
i wood in lengths of 2 or 3 feet — or of ordinary cordwood 
e, 4 feet in length, if the generators are large — is placed 
top of the coke. The wood is ignited, and the gas is 
Livered to the scrubbers and holders in the usual manner. 
> steam is admitted at the . top, however, as the wood 
ually contains a sufficient amount of moisture to render 
- gas of proper quality. 



54, Foundations for Producers. — The foundations for 
►duccrs should be built in accordance with plans furnished 

the makers. As a rule, it is necessary to set both the 
Kjucer and the scrubber on slightly elevated platforms of 
ck or concrete, to raise the apparatus to a level where it 
1 be easily accessible to the operator and to bring the 
*ious parts of the system in proper alinemcnt, so that the 
>es and fittings furnished by the maker will connect as 
onded. Special cases may occur where the conditions are 
'h as to require some deviation from standard plans, and 
such instances the manufacturer of the apparatus should 

consulted and his recommendations and suggestions 



Upon the arrival of the machinery at the place where it is 
to be installed, it is well to examine all the parts for defects 
and to clean thoroughly all vessels, castings, tanks, etc., of 
any packing material, dirt, or sand left accidentally in the 
castings at the foundry. This suggestion applies to the 
various parts of the gas producer, as well as to the pipes and 


26. Firebrick. — Where the firebrick lining consists of 
special shapes, as is the case in most suction producers as 
well as in small sizes of pressure producers, the bricks 
should be carefully examined and any that are damaged, 
broken, or cracked, rejected. As a rule, a few extra bricks 
of each size are furnished, to allow for possible shortage of 
material that may be caused by the accidental breaking of 
some of the bricks while in transit 

Before attempting to place the lining in the producer 
shell, it is advisable to set the lining up on a floor or any 
other level place outside the shell, and to make sure that 
the various bricks fit without leaving excessively large 
spaces or crevices. If necessary, the bricks should be 
ground to each other, so as to remove any irregularities in 
shape and to reduce crevices to not more than -J- inch at the 
joints. It is also necessary to see that the size of the lining 
is in accordance with the producer shell, that the circle 
formed by the bricks is not larger in diameter than the 
shell, and that, when making proper allowance for mortar, 
the total height of the lining will be such as to bring it up 
to the desired level inside of the producer. 

26, Mortar. — After leveling the producer on its foun- 
dation, the laying of the firebrick lining may proceed. In 
preparing the mortar, care must be taken to use a grade of 
fireclay that will withstand tlic heat of the fire. As a rule, 
the manufacturer of the apparatus supplies the clay to cor- 
respond with the material used in making the bricks. The 
mortar is made -of fireclay and water, and should be of about 


the consistency of the cement mortar used in laying bricks 
for foundations. It is of great importance to work the mor- 
tar thoroughly, so as to make it smooth and of uniform com- 
position. There should not be more than a layer of | inch 
in thickness between the various courses of bricks. 

Any openings or fissures that show on the inner surface of 
the lining, and that are therefore exposed to the heat of the 
fire, must be filled with a smooth pulp made of fireclay, asbes- 
tos, and water, of about the consistency of ordinary putty. 
This pulp will withstand the action of the hot fire, while 
mortar made of fireclay and water alone would crumble and 
fall away in a short time. The pulp must be rammed tightly 
into all fissures, and the whole inside of the lining smoothed 
up if the irregular shape of the bricks requires it. 

It is of the utmost importance to have the inner surface 
of the lining as smooth as possible, so as to prevent clinkers 
from adhering to the wall. It also prevents the poking 
tools from catching in the joints of the brickwork and dam- 
aging the lining, when trying to remove the clinkers. 

37. Filling: Between lilnlngr and Shell.— The lining 
is usually insulated from the shell of the producer by having 
the space between the bricks and the metal filled with a 
suitable material. Sand has been used, and if of the proper 
g^ade it will answer the purpose very well. The best sand 
for this purpose is molders* sand that has been used in the 
foundry for making iron castings. A much better material, 
however, although slightly more expensive, is mineral wool^ 
which can be obtained at low cost almost anywhere. Min- 
eral wool is made by subjecting molten slag to a strong 
air blast, the cooled product having a porous, fluffy appear- 
ance resembling cotton. Sand has the disadvantage of being 
liable to run' out of any cracks that accidentally develop in 
the brick lining. This of course would necessitate taking 
enough of the producer apart to be able to replace the sand 
lost in this way. Mineral wool will stay in place as long 
as the lining lasts, and the freedom from danger of a 
shut-down, such as might occur where sand is used, will 


more than pay for the additional first cost of the mineral 

28, Before filling the space between the lining and the 
shell, all the fissures around the fire-doors and the annular 
space around the bricks should be filled first, with a pulp 
made of fireclay, asbestos, and water, the same as that used 
for smoothing up the inner surface of the lining. Next the 
space should be filled with this pulp to a depth of several 
inches and then the mineral wool used up to within 2 or 3 
inches of the top of the lining. The remainder of the space 
is then filled with pulp like that used in the bottom. This 
makes the whole space tight against leakage and keeps the 
insulating material in place, as the pulp will become hard 
after the fire is started in the producer. When putting in 
the mineral wool, it should be packed tight with a suitable 
tool as soon as a small quantity has been applied, and the 
ramming should be continued until the desired space is 
filled, so as to form a homogeneous mass of insulating^ 
material. After the lining and filling are completed, the top 
of the producer may be put in place. 


29. After the' scrubber has been placed in position, le v^ — 
eled up, and properly alined with the producer, the cole. ^ 
that is generally used as a purifying agent should be plac^ <i 
in the scrubber. In doing this, care should be taken not "^lo 
break or grind the coke, and thus make dust and small piec^^s 
that will pack the coke tight and interfere with the flow of 
the gas through the scrubber. When the scrubber is to ^M)e 
entirely filled, the pieces of coke should be selected caref xx ^ly 
as to size and the larger pieces placed in the bottom, the s^S^ze 
gradually diminishing toward the top. The lower portm on 
of the scrubber may contain pieces of about 4 inches in s£ ^e, 
while nothing smaller than 1^ inches should be used at * lie 
top. To avoid breaking the coke in handling, it should be 
let down into the scrubber by means of a basket, a second ^ 


rope being fastened to the bottom of the basket, so that it 

can be tilted and emptied when it has reached the bottom. 

Another equally good method is for a man to stand on a 

'^oard in the bottom of the scrubber and distribute the coke 

^ter it has been lowered into it The contents of the scrub- 

^r should reach up to within about 6 inches of the lower 

^€re of the gas-outlet pipe connected at the top. 

Any coke that may accidentally fall through the scrubber 
^^te should be removed from the space below the grate be- 
for-^ the scrubber doors are finally closed. If this is not 
^t^ended to, some of the small particles of coke may be 
^^^ed into the pipe connections and cause trouble by 
^^^^ging them. 


30. In making the pipe connections between the various 
I^^rts of the apparatus, sharp bends should always be avoided, 
^ they produce unnecessary friction and thus retard the flow 
^f the gas in the pipes. Retarded flow is especially objec- 
tionable in connection with suction gas producers, and it is 
^f considerable importance to provide long-sweep elbows 
^ther than the ordinary cast-iron fittings. As producer gas 
Always contains some impurities before it passes through the 
Scrubber, it becomes necessary to clean the connecting pipes 
^nd fittings regularly. After leaving the scrubber, the gas 
^^ay still contain a small amount of dust or tarry matter that 
"Will accumulate in the pipe connections. To enable the 
X^ipes to be cleaned without taking them apart, the fittings 
Should be provided with handholes and removable covers, for 
"^be purpose of making their interiors accessible. 

31 • The flue valve in the waste pipe that branches off 
Crom the connection between the producer and scrubber is 
xnore liable to become clogged by impurities than any valve 
\)eyond the scrubber. This valve must therefore be arranged 
so that it can be easily taken apart to be cleaned and lubri- 
cated. It is desirable to provide a drip pipe and valve below 


the flue valve, for draining any water that may collect in the 
smoke pipe either from the atmosphere or by condensation. 

32. In order to have the smoke pipe constructed so as to 
give a good draft, which is essential in keeping the fire alive 
over night when the plant is shut down, it should be run in 
the shortest and most direct way possible. The general 
arrangement of the smoke pipe is of course governed by 
local conditions, but it should not have any sharp turns nor 
nm horizontally for any length. If it is necessary to have a 
short length of horizontal pipe before the stack turns verti- 
cally, there should be a drain provided at the bottom of the 
elbow where the turn is made. The vertical length of the 
smoke pipe must be sufficient to insure a strong draft, and 
if there are any buildings in the vicinity the top of the pipe 
should be carried several feet above the top of such build- 
ings. If this is not done, the gases that will escape from the 
stack while the fire is being started might cause annoyance 
to tenants of such buildings. 

If the smoke pipe is led into an old chimney that has been 
used before, it should be carried up through the entire length 
until it reaches the open air. This is of special importance 
if any stoves are connected to the same chimney, because, if 
a fire was lighted in one of the stoves, gas issuing from the 
smoke pipe into the chimney might be ignited and result in 
a violent explosion. 


33. Whether the producer is of the pressure or of the 
suction type, it is equally important that the apparatus itself 
as well as all pipe connections be made absolutely tight. 
Neglect in this respect would cause leakage of gas in the 
pressure producer and result in danger to the health and life 
of persons in the producer room. While this danger does not 
exist in the suction producer, owing to the fact that the 
pressure in this type of apparatus is always below that of the 
atmosphere, small leaks would cause air to be drawn into 
the apparatus from the outside and result in weakening the 


gas and in rendering it ot such quality as to prevent good 
results from its use in the engine. If the leak is very seri- 
ous, the gas would become so poor as to cut down the power 
considerably and eventually stop the engine. 

34. Before attemptmg to make gas, all the joints and 

connections should be tested. A safe method of doing this 

is to generate pressure in the apparatus by closing the valves 

and operating the blower provided for reviving the fire. By 

attaching a small pressure gauge at a convenient point before 

the pressure is raised, and letting the apparatus stand for a 

while afterwards it can be determined whether there are any 

leaks. If the gauge shows a fall in pressure, it is necessary 

to investigate and locate the place at which the leak occurs. 

£ach part of the apparatus can be shut off from the others, by 

means of the valves provided, and the point of leakage can 

t.1ias be accurately determined. When the leak is located, 

it should be stopped. 

The parts most likely to become leaky are the coal-charg- 
ing device and the fire and ash-doors. In handling the fuel 
snd the ashes, it is Almost impossible to prevent impurities 
:f rom settling upon the surfaces of the doors and charging 
apparatus. It is therefore advisable to always clean these 
surfaces after fuel has been admitted or ashes or clinkers 
lave been removed. 



35* After it has been ascertained that everything about 
the apparatus is in good working order in accordance with 
the directions, the producer is ready to be put in operation. 
To start the fire, the generator should be filled, to a height 
of about 18 inches above the grate, with dry, non-resinous 
wood, or with charcoal. A small quantity of cotton waste 
soaked in oil and placed upon the grate under the wood will 
aid in starting the fire. If 'fat pine — sometimes called fitfcA 


pine^ on account of the amount of pitch it contains — or a 
similar wood is used to ignite the coal, a smaller quantity 
will be sufficient. In case the wood contains much pitch, 
no gas should be permitted to pass into the scrubber until- 
the wood has been entirely consumed. 

36, Before lighting the fire, the evaporator should be 
filled, and a small amount of water allowed to overflow into 
the ash-pit. The water-seal box should also be filled, and 
the water supply turned on in the scrubber as soon as the 
fire is started. The valve in the smoke pipe must be 
opened and the top of the hopper closed before lighting the 
fire. After igniting the wood, the ash-doors, fire-doors, and 
the pipe suppljdng moist air from the evaporator to the bot- 
tom of the producer must be closed. The connection 
between the blower and the producer is then opened, and the 
blower started, turning it either by hand or by power, as 
the case may be, unt^l the wood is burning freely. Follow 
this by filling in- about 8 to 12 inches of coal and continue 
blowing for a while until the fire is burning brightly. After 
this, the producer and hopper should be practically filled to 
the top with coal. Continue the operation of the blower 
until the gas at the test pipe between the producer and the 
scrubber bums steadily with a bright blue flame. Then 
close the communication between the blower and the pro- 
ducer, and quickly remove any ashes or clinkers that may 
have been deposited upon the grate. While doing so, the 
fire-doors through which these ashes are. removed should be 
kept open no longer than is absolutely necessary. 

37. Now reestablish communication between the blower^ 
and the producer and again operate the blower for a shorts 
time until the gas, by burning steadily with a blue flame,^ 
proves that it is of the proper quality. As soon as this i^ 
the case, all the apparatus, including the pipe connections- - 
between the scrubber and the engine, should be filled witlt 
gas, thus replacing the air with which they were previously - 
filled. This is accomplished by closing the flue valve an*- 


also the vent pipe that branches off from the gas-supply 
pipe near the engine. The vent pipe is provided for the pur- 
pose of making sure that the whole pipe system up to the 
engine is filled with gas of good quality. 

It will generally require from 10 to 16 minutes from the time 
of starting the fire until all the apparatus is filled with gas. 
There should also be a test pipe provided in the gas-supply 
pipe near the throttle valve on the engine. As soon as a 
trial at this point shows the gas to be of good quality, the 
plant is ready for operation and the engine can be started in 
the usual way. 


38. In order to secure steady and efficient service of the 
plant, it is necessary for the operator to accustom himself to 
performing the series of operations carefully and always in 
the same regular rotation. Experience has shown that the 
following method of procedure gives the best results: If 
the fire requires looking after, the first thing to do is to fill 
in fresh fuel practically up to the top of the hopper, so as to 
replace any coal that has been consumed during the run. 
The second operation should be the poking from the top. 
This is done for the purpose of removing any clinkers that 
may have begun to adhere to the walls of the brick lining, 
^nd also for the purpose of preventing the formation of hol- 
low spaces in the hot bed of fuel known as bridging, 

39. The fire should be poked at regular intervals, as 
determined by the quality of the fuel used and the experi- 
ence the operator may gain while running the producer 
Tinder the conditions of load in each particular case. It will 
:iiot do to neglect removing the clinkers, because, if they 
should be allowed to accumulate on the walls of the brick 
lining in any considerable quantity, it would be impossible 
to remove them while the apparatus is in operation, and 
consequently it would be necessary to shut down the plant 
temporarily and interrupt the service. 


40. The third operation should be the removal of the 
ashes from the ash-pit under the grate. This is generally 
done with a bent scraper. The fourth and last operation 
consists of poking and removing clinkers from the grate 
through the fire-doors. With a stationary gratey a bent 
poker is used for this purpose, afte^ the clinkers have been 
loosened with a straight bar of suitable shape and length. 
This removal of clinkers through the fire-door should be 
done quickly ; in order to prevent an excessive amount of air 
from entering the producer, open one door at a time just 
enough to permit of the removal of clinkers. If the pro- 
ducer is provided with two doors on opposite sides, close one 
door while the other is kept open. The whole operation of 
removing clinkers from the grate should not require more 
than 20 to 30 seconds. 

These operations apply, of course, only to stationai}' 
grates. In producers provided with shaking or rotating 
grates, the cleaning is done by rocking or turning them by 
means of the hand levers or cranks provided for this 


41. The engine is stopped as usual by simply closing 
the gas valve and disconnecting the battery. At the same 
time, in order to stop the producer plant in the proper 
manner, the valve in the vent pipe must be opened at once, 
so as to provide an escape for the gases that continue to 
form in the producer for a short time after the engine has 
been stopped. Next, the hopper of the producer should be 
filled with fuel and the flue valve in the smoke pipe opened. 
As soon as this valve is opened, the valve in the vent pipe 
near the engine can be closed. The water supply to the 
scrubber and producer should then be shut off and the 
valves adjusted that regulate the level of the water in the 
seal and water trap between the scrubber and producer, so 
that the gas will be shut off from the scrubber. Experience 
will show just how far to open the air supply that regu- 
lates the draft necessary' to keep the fire alive over night 


wifhout unnecessary waste of fuel while the plant is shut 

The ashes and clinkers should be removed from the pro- 
ducer, and the fire and ash-doors kept closed. Should it 
become necessary to remove large quantities of clinkers, it 
will be found easier to do this immediately after stopping 
the plant and while the fuel is still incandescent. It is best, 
in such cases, to draw the fire completely and to remove the 
clinkers from above after opening the cover of the hopper. 


43. To start the plant after it has been shut down over 
night, it is necessary only to remove from the grate any ashes 
or clinkers that may be deposited during the night, and to 
operate the blower until the gas bums with a bright blue flame 
at the test tube between the scrubber and the engine. 
Then open the vent and the scrubber valves, see that the 
hopper is closed tightly, and start the engine in the usual 


43. It is always advisable to attend to the cleaning of 
pipes and fittings in the day time, so that it will not be 
necessary to use a light, as a flame brought too close to the 
apparatus might ignite the gas. It is also advisable, as a 
matter of precaution, to have more than one person present 
w^hile the cleaning is being done, so as to guard against 

The building or room in which the producer is located 
should be well provided with ventilators, so that any escap- 
ing gas will be quickly carried away. The gas is very pois- 
onous, and, if it accumulates, is liable to render the work- 
men unconscious and may cause deatli. Hence special care 
should be taken to avoid breathing it. Under ordinary con- 
ditions it ^411 be found sufficient to have the pipe? examined 
and cleaned once in 3 months. 


44, The contents of the scrubber mav last for a veai*or 
more before they require renewing. If it becomes neces- 
sary to clean the scrubber, the whole producer must, of 
course, be put out of commission. The manholes of the 
scrubber should first be opened, so that any gas contained in 
the scrubber may escape. 1 1 may require about 1 hour or more 
for the gas to stop, after which the coke may be removed. 
Any sediment that may accumulate in the bottom of the 
water-seal box, at the bottom of the scrubber, should be 
cleaned out at least once every other day. 


46, The directions already given for the care of produ- 
cers apply especially to suction producers, but they are almost 
equally applicable to pressure producers, especially in regard 
to the firebrick lining, pipe connections, etc But the 
arrangement of the fuel bed is different in the pressure type 
from that used in the suction producer. Instead of having 
on top of the incandescent fuel a large amount of coal that 
is not burning, the height of the fuel bed is limited to from 
2^ to 3 feet above the ashes when using anthracite, and from 
3^ to 4^ feet when using bituminous coal. This will require 
a pressure for the air blast of from 3 to 4 inches of water. 

If the blast is too strong or the coal too fine, the fuel will 
burn too fast near the walls, and it will be necessary either 
to reduce the blast or to use a coarser grade of coal. To 
keep the fuel bed reasonably solid and avoid the formation 
of bridges or honeycombing, a certain amount of poking, or 
barring, must be done, the frequency of which depends on the 
character of the fuel or the rate at which the producer is work- 
in^. A little experience and careful observation will enable 
the operator to determine just how often the fire needs atten- 
tion, so as to keep it in the best condition for steady service. 

When Slopping a ])ressure producer, no imbumt coal 
should be left on top of the fuel bed; the top layer shoi^dbe 
incandescent. The blast should be decreased just before 


stopping, the poke-hole caps removed, and the escaping gas 
lighted at the open holes. Then the blast may be shut 
off entirely. Air will be drawn into the producer by the 
receding flame, so that the gas in the producer will bum 
quietly without any violent puff. 



46, The use of blast-furnace gas for gas engines is of 
recent origin, and cannot yet be said to have passed much 
beyond the experimental stage. The blast furnace is used 
for melting iron ores and producing pig iron. The furnace 
varies from 40 to 100 feet in height, and from 12 to 26 feet 
in diameter. The fuel employed is coke, and the air blast 
used to promote combustion produces a temperature suffi- 
ciently high to melt the ore, and has a pressure of from 6 to 
15 pounds per square inch above that of the atmosphere. 
The amount of gas that passes from the blast furnace is 
about 150,000 cubic feet per ton of pig iron produced. In 
order that the iron may not combine with oxygen pass- 
ing through the furnace, the amount of air admitted is insuffi- 
cient to complete the combustion of the fuel, and hence the 
gas passing out of the furnace contains a large amount of 
carbon monoxide. Blast-furnace gas, however, is not as rich 
in combustible matter as is producer gas, but it contains 
enough combustible matter to furnish considerable power 
when used in gas engines of suitable design. The average 
composition of blast-furnace gas is about as follows: 

Gas Per Cent. 

Carbon dioxide, CO^ 08 

Carbon monoxide, CO 30 

Hydrogen, H 02 

Nitrogen, N 60 

Total 100 


There is usually present some hydrocarbon that affects these 
percentages to a slight extent. The thermal value of blast- 
furnace gas varies from about 90 to 100 British thermal units 
•per cubic foot, depending on the percentage of carbon mon- 
oxide present. The fact that the gas is low in hydrogen and 
rather high in carbon monoxide makes it desirable for gas 
engines especially designed for its use. It has been found, 
in practice, that the gas from the blast furnace will furnish 
about 50 horsepower continuously for each ton of pig iron 
produced in 24 hours. 

47. One of the principal difficulties to be contended with 
in connection with the use of blast-furnace gas in gas engines 
is the large amount of gritty dust that the gas contains. This 
necessitates very careful and thorough cleaning of the gas 
before it is admitted to the engine cylinder. The gas should 
be as nearly free from solid matter as it is possible to make 
it by any cleaning method now in use. When the gas comes 
from the blast furnace, it usually contains from 4 to 7 grains, 
and may contain as much as 12 grains of dust per cubic foot ; its 
temperature is also high, ranging from about 500® to 1,000® F. 
or more. The amount of dust contained has been reduced 
by some of the best modem cleaning processes to as low as 
.01 grain per cubic foot, and even less, which is said to be 
less than the dust contained in ordinary air. 

When the gas from the blast furnace is not sufficiently 
cleaned before it goes into the gas engine, the dust collects 
on the inner surface of the cylinder, and, as the piston moves 
to and fro, the dust is ground between the piston and cyl- 
inder, thus causing excessive heating and perhaps cutting of 
the surfaces. Sometimes, the dust collects in the combustion 
chamber or valves, becomes incandescent from the heat of 
the explosions, and causes prcignition. 

48, To get the greatest efficiency from the combustion 
of the gas, it should be cool and dry as well as clean. The 
high temperature of the gas causes it to evaporate some of 
the water used in thecleanin«4- process and to carry with it a 


large percentage of moisture. This moisture is detrimental 
to the combustion, but is a great aid in getting rid of the 
dust. The particles of dust are moistened by it, and 
adhere more readily to any surface with which they come in 
contact But the moisture must be removed before the gas 
enters the engine. This is done by cooling the gas, thus 
causing the moisture to condense. As it condenses, it falls by 
gravity to the bottom of the apparatus, carrying with it a 
considerable amount of dust. 

The gas is forced through the cleaning apparatus by a 
steam jet or by some form of fan or blower. 


49. In the earliest blast-furnace gas-engine plants, the 
gas was cleaned by about the same process used in a pro- 
ducer plant. It was found, however, that this process did 
not dean blast-furnace gas sufficiently for use in gas engines. 
Hence the cleaning process was extended by adding scrub- 
bers and rotary washers to the apparatus already in use. In 
some cases, the rotary washer was simply a fan with pro- 
vision for spraying water into the gas; while in others, it 
took the form of an enclosed rotating drum or series of disks 
partly submerged in water. The gas being forced through 
the washer came in contact with the large wetted surface to 
which the particles of dust adhered, and as the surface 
revolved into the water the dust was washed away. A still 
later development is represented by the centrifugal cleaner, 
in which the gas is carried around inside of a casing by a 
revolving drum with projecting vanes, the speed being such 
that the centrifugal force throws the dust against the casing, 
from which it is washed by a spray of water. 

60. Cleaning: Plant With Rotary Washer. — The gas 

IS carried in flues or pipes from the blast furnace to the 
cleaning ' apparatus and engines. It is taken from the 
flue leading downwards from the top of the furnace — known 
as the down-comer — and conducted to a main, which may 


also receive the gas from other furnaces. It then passies 
through a washing process that takes out the larger particles 
of dust and grit. Next, the gas goes through a long pipe or 
series of pipes that reduce its temperature and take out con- 
siderable dust and moisture. In the first washing process, 
the gas takes up considerable moisture, and the dust, becom- 
ing moist, adheres readily to the surfaces with which i^ 
comes in contact. From the long pipes, the gas may pa^ 
through a rotary washer consisting of a fan or a drum wit^ 
vanes on its circumference with a spray of water injects ^ 
into it. The whirling motion given the gas as it pass^^ 
through the fan throws the dust against the casing, to whicr^ 
it adheres and from which it is washed into a water outlet If ^ 
the injection water. From the fan or rotary washer, theg^-^ 
may pass through other scrubbers or washers similar to th- 
coke scrubber or sawdust cleaner described in connectio 
with the producer-gas plant. Sometimes, two scrubbers 
cleaners are used, in which case the gas passes first through 
coke scrubber and then through a sawdust cleaner forremoV^ ' 
ing the finer particles^f dust. From the last cleaning process* 
the gas is taken in many plants to a gas holder of considec 
able size, where the remaining moisture in the form of vapc^^ 
is condensed by cooling and settles with the remaining dust 

From the gas holder, the gas is conducted directly to th»^ 
engine cylinder. The gas holder serves the double purpo^;^ 
of a cleaner and a regulator or equalizer of the pressure <::>f 
the gas delivered to the engine. The pressure of the g^s 
in the holder will usually vary from 1 to 2 or more ounces 
per square inch above atmospheric pressure. 

When the rotary washers are properly designed axad 
installed, the scrubbers between the cleaner and gas holder 
and the long pipes may be dispensed with, thus reducing the 
size, first cost, and operating expenses of the cleaner plant. 
Furthermore, the gas is cleaned much better than in the 
cleaners used on producer- gas plants. 

51. Centrifugal Cleaning: Plant. — In the cleaning 
plants that have given the best results with European 



blast-furnace gas, a rotary or a centrifugal washer fonns 
the principal part. In some plants, large, slowly tam- 
ing washers are used; while in others, small and rapidly 
turning centrifugal washers are employed. In the first, ilie 
cleaning is done by bringing the gas in contact with a lung 
revolving surface that dips into the water at every revolu- 
tion, thus washing off the collected dirt and wetting the sur- 
face. In the second, the gas is driven by centrifugal force 
against the sides of the casing and the dirt washed out with 
a spray of water. 

A centrifugal plant for cleaning blast-furnace gas is shown 
in Fig. 7. Before the gas reaches the centrifugal cleaner, it 
is passed through a dry stationary dust catcher, or cleaner, ' 
where larger particles of dust are removed. The stationary 
cleaner may be siinply a large closed drum in which the 
velocity is low and the dust is allowed to settle out by grav- 
ity; or it may be a smaller drum and contain deflectors for 
changing the direction of motion of the current of gas. From 
the dust catcher, the gas passes down through the pipe a to 
the centrifugal cleaner t>. The interna! dnim of the centrif- 
ugal cleaner revolves at about 850 revolutions per miniite, 
thus producing sufficient velocity in the gas to cause the por- 
ticlesof dust and dirt to ily outwards against the casing, tinder 
the influence of the centrifugal force. The gas usuallycanies 
from 1 to 3 grains of dust per cubic foot as it leaves the dn" 
cleaner, and the centrifugal cleaner reduces this amount lo 
about .01 grain per cubic foot before the gas leaves. The 
moisture in the gas, however, is increased, and for this reason 
the use of a dn.'er or dry filter is found advisable. The centrif- 
ugal cleaner b is driven by a motor c, the gas leaves by the oai- 
lel J, and passes around the baffle plate in e, where someef 
the moisture is precipitated. The gas then passes through the 
pipe _/* and valve ^ to the main A, from which it can be dnrum 
off at different points, as desired. The valve i opens to tiK 
dry filter/, which contains trays carrying slats covered willi 
mineral wool or other diying substance, through which the 
gas passes in the direction shown by the arrows. The dry 
filter is divided into two compartments by the partition k. 



the g:as passing through one tray of mineral wool in each 
conapartineiit, leaving it comparatively dry. The valve i 
regulates the opening to the main tn, which conducts the gas 
to a holder or directly to the gas engines. 

5S. The Centrifugal Cleaner. — ^A larger view of the 
centrifugal cleaner is shown in Fig. 8. The blast-furnace 
gas enters the cleaner through the opening shown at a. 
The casing b remains stationary, while the drum c is keyed 
to the shaft d, with which it revolves. The small vanes e 
are arranged in the form of a spiral around the drum c, so 

that the gas must pass through a long passage or be thrown 
against the outer casing as the drum revolves. The gas 
leaves the washer through the outlet f, and passes to a dry 
filter, as previously described. Water is sprayed against 
the revolving drum through the inlets g, and is carried 
around by the vanes of the drum with sufficient speed to 
keep the casing wet and furnish water for washing ofE the 
dust as fast as it collects. The dirty water passes out 
through the water leg h to a drain. 

The gas that enters the cleaner is still hot, sometimes 
having a temperature as high as 300° or even 400° F, It 
consequently vaporizes some of the water when it first 
comes in contact with the wet surfaces of the centrifugal 


cleaner. This vapor mingles with the dust in the gas, and 
the centrifugal force throws the vapor and dust outwards, 
causing them to come in contact with the outer casing, to 
which they adhere. A wire screen is located inside the 
casing where the injection water enters, so that the water is 
at once broken up into fine particles, offering more surface 
to the dust and being more easily vaporized. The tempera- 
ture of the gas is also reduced by the water, the amount 
varying from 60° to 260° F., depending on the temperature of 
the blast-furnace gas, the temperature of the water, and the 
efficiency of the cleaner. It is customary to keep the water 
stored in elevated tanks, and feed it to the washers by grav- 
ity and to discharge it into clearing ponds. The dust and 
dirt are allowed to settle out of the water, which is then 
pumped through cooling coils back to an elevated tank, 
from which it again flows to the cleaner by gravity. The 
water is thus cooled and cleaned, and hence can be used 
over and over again with the addition of a small amount of 
fresh water. 





1. The owner or chauffeur who for the first time takes 
charge of an automobile must, especially if the machine is a 
new one or of an unfamiliar type, make a searching exam- 
ination of the condition of the automobile tefore it will be 
prudent or even safe for him to attempt its operation. This 
examination should not be limited to the engine and its 
accessories, but should include all parts of the car. In the 
following articles, attention is directed to the parts of the 
engine that should receive careful attention. 

3, In the first place, a general survey of the engine 
should be made — particularly if it is of an unfamiliar type — • 
special attention being given to the location and mode of 
action of each individual part included in the valve mechan- 
ism, the ignition mechanism, and the governor, pump, radi- 
ator, carbureter, etc. Attention should be given to the steps 
necessary to be taken in order to expose, for examination, the 
working parts of the engine, such as, the two- to-one gears (if 
thesie are enclosed), the pump, the cams, the igniters (if these 
are of the contact variety), the magneto (if any), and the 
interior of the crank-case, so far as this can be reached 

Qfpyri^kiedby Jnternationai Textbook Company. Entered at Stationer f Hall^ London, 




without dismantling the engine. On completing this pre- 
liminary investigation, the condition of the various 
should be examined in detail. 

3, The float valve of the carbureter should be tested 
leaks by opening the valve between it and the tank an 
looking for gasoline drip. If gasoline escapes, it may siir^ 
ply be because the float is set too high, so that it does 
close the needle valve before gasoline issues from the spra^ 
nozzle. Or, it may be that the valve itself leaks. 

At this stage, it is well to assume that the float is prop^ 

erly adjusted, and to begin by shutting off the main gaso^^^ 
line valve, and then unscrewing the washout plug below th 
needle valve. It may be found that dirt, waste, or a splin-^ 
ter of wood has got past the strainer, through which, pre- 
sumably, the gasoline passes on its way to the float, and is 
lodged in the needle-valve opening. It may be of advan- 
tage to open the top of the float chamber, which can usually 
be done without disturbing other parts, and take out the 
float and needle valve. A little gasoline washed down 
through the needle- valve orifice will then generally carry away 
any dirt that may have clung to the valve when the plug 
was unscrewed. If the gasoline still drips when the parts 
are reassembled, the mixing chamber should be opened and 
the top of the spray nozzle examined to see if gasoline is^ 
escaping from it. An electric light should be used in mak- 
ing an examination of the carbureter, as, with any othe 
illuminant, a fire might be started. The portable electri 
flashlights sold everywhere at a moderate price answer th 
purpose very well. 

4. If gasoline is escaping from the spray noxzle, th 
needle valve of the float may be carefully ground in, b 
placing between the valve and its seat a paste made of po 
dered grinding material and oil or water, using for this pu 
pose either very fine sand, or, preferably, pumice or rotte 
stone. The method of regrinding valves will be explainer" 
more fully in Troubles and Remedies, Emory should n 
be used, as it will embed itself in the brass valve or seju 


A little of the sand or pumice should be mixed with oil to 
make a paste. The mixture is applied to the needle point, 
which is then rotated by quarter turns in its seat with slight 
pressure, taking care to keep the stem as nearly vertical as 
possible and frequently adding fresh paste. 

If this does not stop the leaking, it is likely that the float 
is too high ; but, unless the gasoline escapes very rapidly, it 
is better not to disturb the float until attention has been 
given to other more important details. The car, however, 
should not be left standing with the main gasoline valve 
open, for the dripping gasoline may catch fire from the 
lamps, from a stray spark in the ignition circuit or at the 
timer, or from a match accidentally dropped near the valve. 

The manner of adjusting the carbureter should be noted, 
but the adjustment should not be disturbed unnecessarily, 
as it is often hard to get the right mixture after this has 
been done. 

6, Next to making sure that there are no gasoline leaks, 
the most important thing is to see that no bearings are too 
tight or have seized, owing to lack of oil or the bending of 
the shaft or connecting-rods. The compression relief cocks 
should be opened and the shaft turned over slowly by hand. 
The shaft should move with entire freedom, a little more 
easily at the beginning and end of the piston stroke than at 
raid-stroke, because of the slower movement of the piston 
at the ends of the stroke, but with no binding or sticking at 
any point. If the shaft turns hard, the car should be 
taken to the repair shop, since probably either the bearings 
or the pistons are cut, or the shaft or rods are sprung out of 
true, as, for .example, from having struck a loose nut or 
other obstruction in the crank-case, or from preignitions in 
the cylinders. Fortunately, serious trouble of this sort does 
not often occur. 

At the outset, it is well to locate all loose bearings, since 
these require more lubrication than properly fitted bearings. 
If they are very loose, there is a strong likelihood that they 
have been cut, in which case they ought to be opened, 


scraped, and refitted at the earliest possible moment. 0[ 
the main-shaft bearings, that next to the flywheel is the 
most likely to be loose. If the engine is vertical, 3 jack 
may be put under the flywheel and the jack-lever worked 
gently up and down to disclose looseness, if any, in this 

G. To expose the crankpin bearings of a vertical motor, 
it is sometimes necessary to take down the. bottom half of 
the crank-case, which is generally attached to the upper 
half by capscrews or studs, and which simply serves the 
purpose of an oil pan. Under this arrangement, the shaft 
bearings are usually supported from the upper half of the 
crank-case, which is itself supported on the frame of the 
car. Nevertheless, it is advisable, when slackening the 
screws or the nuts on the studs, to find out whether or not 
they are carrying the weight of the crank-shaft. This caa 
be done by slackening all the screws several turns, and then 
pushing upwards against the oil pan with the hand to see 
how much pressure is necessary to lift the pan off the 
screws. If the shaft is found to be resting on them, it will 
be better not to take it down at once, unless it is evident 
that the main-shaft bearings themselves need attention. 
Generally, if the shaft is supported by the bottom half of 
the case, the crankpin bearings can be reached from hand- 
holes located in the bottom or sides of the crank-case. 

The crankpin bearings can be tested for lightness by set- 
ting the engine at mid-stroke and oscillating the flywheel 
very gently back and forth while the fingers of one hand att 
resting on the edge of the crankpin bearing. A sligbt 
looseness may be allowed, provided the lubrication is suffi- 
cient, and there is no cause to suspect that the bearings have 
been cut, The amount of permissible looseness \v^U depend 
to a great extent on the particular engine and the speed at 
which it is to run. A vertical four-cylinder engine running 
at moderate speed will bear as much as .002 inch of lost 
motion on the crankpins, but if the same engine is run at a 
high speed this will be too much. 


7. The main-shaft bearings will bear less lost motion 
than the crankpins, and if one bearing is worn more than 
another, as is likely to be the case, it will result in one-sided 
wear of the crankpin bearings, due to the settling of the 
shaft. The main-shaft bearings ought not to have more 
than .001 inch of play before being taken up, but more than 
this is often found. 

A double-opposed horizontal engine will, sooner than any 
other type, develop a pounding sound, generally called a 
poundy at the main-shaft bearings, owing to the fact that the 
explosions occur alternately in opposite cylinders, and there 
is nothing to keep the shaft against one or the other side of 
its bearings. 

8. In addition to the inspection tor loose bearings, the 
principal nuts and screws should be tested to see that they 
are tight, and if any cotter pins are missing from bolts, 
studs, or slotted nuts, they should be supplied at once. The 
bolts on the crankpin bearings should also be examined for 
tightness, and to see that cotter pins are supplied. 

9. If the inlet valves are automatic, see that they work 
freely in their guides, that they do not leak, and that their 
springs are not too weak. If there is more than one cylin- 
der, the inlet-valve springs must be alike in tension. If the 
valves stick, they may be freed by squirting a spoonful of 
gasoline on them. If they leak, they should be ground in, 
as described later. 

The openings of the valves should be determined to some 
extent by their diameters. Valves up to 2 inches in outside 
diameter generally lift about \ inch, and slightly more than 
this if they are larger. The keys through the valve stems 
should be examined to see that they are not on the point of 

The tensions of the valve spring on similar valves of the 
same engine should be equal; their equality may be tested 
by pressing the ends of the valve stems together while the 
valves are held by their cages, as shown in Fig. 1. The 
valves should begin to open with about the same pressure. 


I and should also reach full opening with equal pressures. 1/ 
I one spring is weaker than the others, it may be taken ofl 
and stretched gently. Too great a lift makes the valvi: 
sluggish in closing, and permits a portion of the fresh 
charge to be forced backwards through the valve at the 
beginning of the compression stroke; this prevents the 
engine from attaiDin^ 
its maximum speed. 
When the valve open 
ing is too great, 't 
may be reduced by 
sltppmg a washer 
o\er the stem. For 
this purpose, BOinc 
sort of a spring 
washer is preferable, 
but not essential A 
makeshift of soft wire 
will not do, as the hammering of the \alve will soon break 
it, and a bit tit wire may make a great deal of trouble by 
getting into the cyHnders. 

10. The user should satisfy himself regarding the Inbri- 
' cation of every part of the engine. Every oil pipe shoulil 
be traced, and every oil cup and oil hole located and the 
purpose of each ascertained. Oil pipes leading from the 
automatic lubricator should be disconnected close to the beflT- 
ings or cylinders, and the lubricator worked by hand to see 
that it is feeding properly. Generally, this can be done bj' 
working the pump plungers tip and down to the extent of 
the lost motion on the pump eccentric. If this cannot be 
done, the delivery of oil may be watched after the engine 
has been started. 

If an oil pipe is clogged it should be disconnected close to 
the lubricator; and if no oil comes from the lubricator at that 
point the cause of stoppage should be located. The trouble 
will probably be fonnd to be caused by dirt or waste under the 
check-valves of the pump. If oil comes from the lubricator 


when the pipe is disconnected, the latter is stopped up, and 
can be cleaned by running a wire through it. Generally, how- 
ever, any obstruction of this sort will travel to the end of the 
pipe and lodge in the check- valve, if there is one at that 
point, so that the check-valve should be unscrewed and 

11. The manner in which oil is supplied to the crank- 
pins should be ascertained, since these are sometimes fed 
simply by internal splash and sometimes by centrifugal ring 
oilers and oil passages drilled through the cranks. If inter- 
nal splash is relied on, the user should see that the crank- 
case contains enough clean oil to allow the connecting-rod 
caps to dip into it about ^ inch at the lower end of their 

If the car has not been used for a considerable time, the oil 
in the crank-case, oil cups, and reservoir is likely to be stiff 
and gummy. ^ If this is the case, the oil should be drawn off, 
and a moderate quantity of kerosene used to make sure that 
the oiling system generally is thoroughly clean. Before 
starting the motor, a liberal supply of fresh oil should be 
provided, as the kerosene will cut away the old oil wherever 
it reaches, and the pistons, cylinders, and bearings might 
become cut before the fresh oil can reach them from the res- 
ervoir. When oil has not been cleaned out in this manner, it 
is a good precaution, on general principles, to put a pint or a 
quart of fresh oil into the crank-case. If, however, on start- 
ing the motor it is seen that a considerable quantity of white 
smoke is being produced, the crank-case has evidently too 
much oil, and a portion should be drawn off. 

13. The ignition circuit should next be gone over. This 
should be done with the switch closed and the safety plug — 
that is, a plug the removal of which will break the circuit 
— if one is used, inserted in the switch or coil, the gasoline 
shut off, and the compression relief cocks (if any) open. The 
positions of the lever controlling the spark for early and late 
ignition should be ascertained by a careful examination of 
the timer, and the lever should be set for a late, or retarded, 


spark, as a precaution in case of any accidental explosion in 
the cylinders. The engine should be turned over slowly, 
and the sound of each of the vibrators on the coils noted 
The sound should be clear and regular, and fairly high with- 
out being tinny. If necessary, the contact screws, or the 
tension screws, if there are any, of the vibrator springs 
should be adjusted until the vibrators sound alike. 

13. The timer should be examined to see that the con- 
tact segments are not badly pitted by the spark at the leav- 
ing edge. If they are pitted, or if the fiber or hard rubber 
adjacent to them is roughened by the sparking, the timer 
should be cleaned upas well as possible with a piece of sand- 
paper or a file, and the first opportunity taken to true it in 
a lathe. If the timer is rough, the contact roller pr fingers 
will jump and give very erratic contact when the motor is 
running fast. 

The spark plugs should be unscrewed and their condition 
examined. It is not necessary to take them apart unless 
they need cleaning, or unless it is discovered that the porce- 
lain is broken, which will be evident by a looseness of the 
outer end. If the porcelain is broken and there are spare 
porcelains at hand, the bushing may be unscrewed and a 
new porcelain and gasket inserted. Usually, it is impracti- 
cable to use the old gasket a second time, as the bushing has 
to be screwed down so tight as to endanger the porcelain. 
The bushings should be set down sufficiently to prevent leak- 
age past the porcelain, but no more. 

14. The gap between the spark points should not be 
greater than ^V inch for the best possible spark. The points 
should be presented directly to each other, and should be filed 
t:ue and square. The spark will not be so intense if it jumps 
between needle points. If necessary, the porcelains should 
be cleaned. To do this properly, it is generally necessary to 
take the ping apart. The porcelains are cleaned with a cloth 
or brush wet in gasoline. If the carbon deposit is very hard, 
it may be loosened with fine emery cloth and the cleaning 
finished with gasoline and a cloth. In assembling the plug, 


care should be taken that the spark points are restored in 
their correct relation to each other. 

15, The battery may be weak and may have to be 
reoharged or replaced. If dry cells are used, it is likely that 
some of them are weaker than others. The only way to 
determine this is to use a battery tester, which is a small pocket 
ammeter through which the cell may be momentarily short- 
cix^cuited. The battery as a whole may be tested by discon- 
necting one of the secondary cables from the spark plug and 
noting the length of the spark in the open air. The spark 
sliculd be at least f inch in length — \ inch is better. The 
coil should not be worked with the detached cable held so far 
from the motor that no spark can jump, as this is liable 
to tax the insulation of the secondary winding. 

16. Having gone over the engine, it may be started, to 

determine whether the ignition and carbureter adjustments 

have been made properly. Set the throttle so that the motor 

does not run excessively fast, and listen to the sounds it 

^akes. Any knocking sound should at once be traced to its 

source and eliminated. The sound may be due to a loose 

mud-guard or something of the sort on the car, which of 

course does not affect the engine. Or it may be found in 

the loose coupling between the clutch and the gear-shaft, but 

this coupling is intended to be loose, and will give no trouble. 

Any knock due to a loose bearing or loose bolt, however, should 

at once receive attention. It may be found that the motor 

will run light — that is, without driving the car — and with the 

throttle nearly closed without developing a knock, but may 

^ock badly when under load. This subject is taken up in 

T'^oubles and Remedies, 

17. The sound of the impulses should be listened to; also 
t^e sound of the exhaust at the muffler. If the engine has 
several cylinders, the impulses should be equally timed and 
should take place with equal force. If, with the spark some- 
what retarded, the impulse is more energetic in one cylinder 
than another, which may generally be told by the muffled 


sound of the explosion, it is either because ignition takes 
place too early in the cylinder, or because a deposit of car- 
bon in the combustion chamber ignites the charge in its own 
vicinity immediately after the spark, so that the charge is 
burning from two points at once and consequently more rap- 
idly than it should. Actual preignition, that is, too-early 
ignition, due to carbon deposit, seldom occurs when the 
engine is running light, but may occur when the car is run- 
ning. If early ignition in one cylinder is due to faulty 
timer adjustment, the difficulty may be corrected in some 
one of several ways, according to the construction of the 
timer. Sometimes the adjustment must b6 made by filing 
the contact segments. This should, however, be attempted 
only as a last resort, after it has become evident that the 
trouble is not caused by heated carbon in the cylinder, or 
causes that can be corrected in some other way. 

18. If the inlet valves are automatic, they are likely to 
work unequally when the motor is running light with the 
throttle nearly closed. Under these conditions, the most 
careful equalizing of the springs will not prevent one or two 
cylinders from assuming most of the work, because the 
force available to open the valves is so small. Often, an 
engine will run on one or two cylinders for some time in 
this manner, and then for no apparent reason some other 
cylinder will start working, and the first will stop. As soon 
as the throttle is opened, all the cylinders begin to work 

19. When the engine is running light, a late ignition in 
one cylinder will show itself by a louder exhaust from that 
particular cylinder, owing to the slower combustion of the 
charg^e, and consequent higher pressure when the exhaust 
valve opens. The remedy for late ignition is practically the 
same as for early ignition, any adjustment of the timer being, 
of course, in the opposite direction. 

20. A quick method of testing the spark timing is as 
follows: Shut off the gasoline, retard the spark as far as 


possible, and open the compression relief cocks. Turn the 
crank slowly by hand, letting the air escape through the 
cocks so that the compression will not cause the pistons to 
run ahead, which would take up the slack between the 
crank-shaft and the timer, thus giving a false result. Note 
the position when the vibrator begins to buzz, and mark the 
rim with chalk or otherwise. Now turn the crank, always 
forwards^ until the next vibrator begins to work, and note 
the flywheel position again. If the engine has four cylin- 
ders, or two vertical cylinders with opposite cranks, the new 
position should be exactly one-half a turn from the old. If 
the engine has two opposed cylinders, or two vertical cylin- 
ders, with the cranks together, the flywheel should have 
made exactly a complete revolution. If there are three 
cylinders, the marks on the flywheel should be one-third of 
fhe rim circumference apart. Many modem cars have the 
flywheel rims already marked to indicate the top and bottom 
positions of the cranks, and these marks may be used, as the 
spark should occur exactly at the outer or upper dead cen- 
ter when fully retarded. 

In case the spark timing is found to be very irregular, it 
is best to attend to it at once, and in any case irregular tim- 
ing should not be neglected, as it involves a considerable 
loss of power. - 

21. While the motor is running, note whether the cool- 
ing water is circulating properly. The motor should be able 
to run indefinitely with the throttle just open and the spark 
about one-half advanced, without the radiator heating up 
excessively, provided that the latter has a fan to assist its 
cooling. If, on taking the car out on the road, it is found 
that the radiator is persistently overheated, the cause of 
such overheating should be investigated. The trouble may 
be found to be due to a clogged pipe, dirt or oil on the inside 
or the outside of the radiator, a defective pump, clogged 
radiator tubes, etc. Before starting, one should always see 
that there is plenty of water in the radiator, as a deficient 
supply will cause overheating. 




22. The ordinary care of a good automobile engin 
when everything is working well, is a very simple matte- rx", 
and comprises hardly anything more than due attention -to 
lubrication, occasional testing of the batteries, with rechar^^:- 
ing or replacement as required, and seeing that the radiat<i3r 
or water tank is kept full. All the oil supply to the lubricr ^t- 
tor and oil cups should be strained, though; as the lubx^- 
cator itself is probably fitted with a strainer, no additioim .s.1 
attention at this point is likely to be required heyowr^d. 
occasionally taking out and cleaning the strainer. If amny 
dirt, bits of wood, or fibers of waste get past the strains r, 
they are liable to make trouble if the oil is fed throu^r^ 
any kind of a check-valve or needle valve. Waste is p^x"- 
ticularly troublesome in this respect, as it shreds and a f^^vv^ 
fibers of it may very easily get into the oil without bei icig 

23 If the engine is fed from a mechanical oiler, the oil 
pipes should occasionally be disconnected near the engine ^ 
and the engine nm or the pump worked by any other avail- 
able means, to determine if the oil is feeding properly- 
Most indiWdual pump oilers are operated by eccen trios, 
which work against stop-screws attached to the plungex"S, 
atui the strx^ke of the plungers is adjusted by turning the^se 
scrvws to allow mor^ or less lost motion between them axad 
the iXXXMUrics, The operator should learn, by experimen t- 
iti): with the |\irtioular kind of oil he uses, what is the le^^^^ 
stroke for oaoh p\i:r*p that will lubricate the engine proper 1 J 
If thotx^ is arv i^Tcat diiTervnce between the strokes tl^'^^ 
vu, it is prx^lv^V.e that there is leakage^ either in ttie 
•jWvkinc arvv.:r,vi the p'v.r.cer that demands the longest strol^e 
tor tlic V i' tVcv,, v^r in the check-valves^ and this leaka^ 
sV.ou\^, Iv ::*.vcs: cvttvV. ,»: v r.ce. 


If the oil is not fed to the pistons in sufficient quantity, 
the engine will make the fact known by a laboring sound 
and a falling off in power, when both the ignition and the 
carbureter are in perfect order. If this occurs, a little extra 
oil may be put into the crank-case, where it will be thrown 
up into the cylinders in sufficient quantity to ease the engine 
until the oiler can be readjusted. A new engine should 
have a little more oil on both pistons and bearings than one 
that has nm several hundred miles, and it is well to feed 
oil to the former until a little white smoke shows in the 
exhaust. Black smoke indicates too much gasoline in the 

24. As elsewhere explained, it is best to use the heavi- 
est oil that the weather conditions will permit. Often it 
will be found that a heavy oil can be used in summer and a 
medium or light oil substituted in winter without a change 
of lubricator adjustment, owinor to the light oil flowing 
more freely. Generally, however, an increase in feed is 
necessary when the lighter oil is substituted. 

25. It is well to squirt a few drops of kerosene into 
each cylinder at the end of a long day's run, say from 75 to 
150 miles. This will loosen any carbon deposit that may 
have formed about the piston rings. Kerosene is a very 
efficient solvent of the tarry products that act as a binder 
for this carbon deposit, although, of course, the carbon itself 
is not dissolved. Most engines have compression relief 
cocks on the cylinder heads that may be used for introduc- 
ing the kerosene ; but if these are absent the kerosene may 
be injected through the inlet valves. 

26. If the splash system of lubrication is used, and the 
oil is fed to the crank-case by a hand pump on the dash, this 
pump should be operated every 25 miles or thereabouts, 
depending somewhat on the amount of low-gear driving 
required. Generally there is a shut-off valve between the 
pump and the crank-case, which is to be opened by hand 
before the pump is operated. 



An improved arrangement that obviates failure of chect- 
valves connected with the hand pump to do their duty con- 
sists of a three-way hand valve that in one position admits 
oil to the pump and in the other permits the oil to pass 
from the pump to the crank-case. This valve is operated 
by hand for each stroke of the pump. The pump, of course, 
is of a fair size, so that two or three strokes are sufficient 
Once in, say, 500 miles, all the oil should be drawn oflE from 
the crank-case, the case washed out with kerosene, and 
fresh oil put in, as it gradually fouls from carbon passing 
the piston, and also gathers grit worn from the bearings. 

27. Beyond attention to the lubrication, the daily care 
required by an automobile engine is simply the brief regular 
inspection to see that ever}' thing is working properly. If a 
battery is used for ignition purposes, it will need replace- 
ment once in a while, and the operator should keep himself 
informed of the battery's condition by occasional tests, so 
that he will not be unexpectedly stranded. The tremblers 
on the spark coils require occasional adjustment, and the 
operator should notice the sound of each one, and file the 
contact points square or readjust the springs or contact 
screws until the sound is correct. 

28. Occasionally, the spark plugs will foul and require 
cleaning or replacement. How often this will occur is alto- 
gether a question of the particular carbureter used, lubrica- 
ting arrangements, and type of plug; and the only general 
directions that can be given are that the operator should 
adjust the lubricator and the carbureter to prodvce as little 
free carbon as possible in the cylinder, and then should 
learn by trial how often the plugs require inspection. 

21), If the car is used in cold weather, special attention 
must be ^avcn to the lubricating and cooling systems. One 
item in the daily care c)f a motor that cannot well be neg- 
lected is the listening for knocks or unusual sounds. These 


xiay occur from a great variety of causes, which are fully 
ireated in Troubles and Remedies, Nearly all the causes 
:liat produce knocking" grow rapidly worse if not attended 
:o, and therefore no symptom of this sort should be neglected. 


30. The regular order for starting an automobile engine 
Is given in the following paragraphs. This order should be 
followed every time the engine is started, for this is the best 
\eay to avoid forgetting things; in fact, the beginner will do 
^'ell to memorize these instructions. 

1. Open the main gasoline valve at the tank. If the 
tank is hung low, and the gasoline is lifted to the carbureter 
by air pressure, ascertain — by priming the carbureter if 
necessary — that the tank has the required pressure, and 
pump air into it by hand, if necessary. A hand pump for 
this purpose is mounted on the dash, usually at the left end 
Sometimes the gasoline passes through a small auxiliary 
tank cm the dash, and this tank holds gasoline enough to sup- 
ply the carbureter by gravity until pressure from the exhaust 
gases can be raised in the main tank. 

2. Retard the spark as far as possible. This is of the 
first importance, as the attempt to start with the spark 
advanced may result in a broken arm. It is an excellent rule 
never to turn the starting crank, even when it is thought 
that no explosion can occur, without first seeing to it that 
the spark lever is retarded. 

3. Set the throttle about one- quarter open. 

4. Close the switch and insert the safety plug, if one is 

6. Turn on the oil feed. It is assumed that any oiling 
and filling of oil cups done by hand has already been 
attended to. 

6. Open the compression relief cocks, if there are any. 

7. Prime the carbureter, by depressing the float or oth- 
erwise, according to its construction. If the motor has been 
stopped for not more than an hour or two, or sometimes 


longer, this is not necessary. If the tank has pressure feed, 
and the carbureter has been primed to test the pressure 
(see 1), it does not need to be primed again. 

8. Engage the starting crank, and turn it over until 
the resistance due to the compression stroke is felt. If the 
starting crank is not now on its up stroke, move it back- 
wards a quarter or half turn until it is, and reengage the 
ratchet at this new point. Never push the crank over the 
compression stroke. Even if the switch is open, a hot motor 
may start from preignition, and a **back kick" may result 
in a broken arm. 

9, Pull the starting crank upwards smartly against the 
compression. The motor may start. If it does not, turn 
the starting crank until the next compression stroke comes, 
and pull it upwards smartly as before. 

31. If the carbureter has not been primed too much or 
too little, the motor should start unless the gasoline is too 
cold to vaporize. If it does not start with the second or 
third trial, prime the carbureter again and repeat the opera- 
tion. If the motor still refuses to start, something may 
have been neglected or forgotten. It may be that the gaso- 
line is not turned on, that there is no gasoline in the tank, 
or that it is stale or heavy, that the switch plug is not in 
place, that the battery is not strong enough, or that the 
method of priming the carbureter has given too light or 
too weak a mixture. The method of priming is something 
that will depend on the individual carbureter, and can only 
be learned by experience. 

33. The procedure for stopping an automobile engine is 
to partly close the throttle so that-the motor will run slowly 
and then open the switch; if the stop is permanent, take out 
the safety plug, shut off the oil feed, and shut off the gaso- 
line at the tank. If the car has been run some distance it is 
well to squirt a small amount of kerosene through the com- 
pression relief cocks to loosen any carbon deposit that may 
have gathered around the piston rings. 




33. When a column of gas moves rapidly, as in its pas- 
sage through the admission or exhaust valves of an engine, it 
T^quires considerable force to bring them to rest suddenly. 
"When the force resisting the flow is small, it requires a con- 
siderable interval of time to bring the gas to rest. This is 
very noticeable in engines having automatic valves, in which 
the force tending to close the valves is small. For this rea- 
son, the valve timing of a high-speed automobile engine must 
be radically different from that appropriate to stationary 
engines. As the beginning and end of the piston strokes 
represent considerable crank-angles with very small piston 
movement, advantage is taken of this fact to hold the valves 
open for a considerably longer time than would theoretically 
be required in order to give the maximum opportunity for the 
movement of the gases. 

The exhaust valve should open at a crank-angle between 
30° and 40° before the end of the expansion stroke. This 
represents from one-twelfth to one-ninth of a revolution, and 
approximately from 5 to 10 per cent, of the piston stroke. 
It is a common practice, with automobile makers, to mark 
the flywheel rim with reference to some convenient fixed 
object, generally the vertical (or horizontal, if the motor be 
lorizontal) center plane of the motor. These marks may 
ndicate the inner and outer dead centers, or they may indicate 
vhat the maker has decided is the suitable crank position for 
he exhaust valves to begin to open. In the latter case, it is 
5:enerally best to adhere as nearly as possible to the point of 
:>pening thus indicated. 

34. Although in the majority of automobile engines, the 
Exhaust valves close at the end, or dead center, of the 


I exhaust stroke, it has been demonstrated conclusively that 
I there is a marked advantage in holding the valves open until 

the crank is 5° or even 10° past the center. The latter angle 
L represents a piston movement of only about 1 pt-r cent of 
the stroke, and no fresh mixture will enter during this 
period; whereas the prolonged opening of the exhaust 
valve permits the gases in the exhaust pipe to create a slight 
suction in the combustion chamber by virtue of their own 
inertia, thus tending to induce the flow of a larger charge of 
fresh mixture. If the exhaust valves are held open unii! 
the crank is about 10° past the dead center, it is unnecessary 
to open them quite so early on the expansion stroke as would 
otherwise be considered necessary. A good average rule is 
to open the exhaust valves 35°, or practically one-tenth of 
the circumference of the flywheel before the end, or dead 
center, of the expansion stroke, thus making the total opening 
of the exhaust valve about 223" of the revolution of the fly- 
wheel. If the engine is to run at speeds upwards of l.fiOO 
revolutions per minute, an earlier opening and later closing 
may be of advantage. 

35, If the inlet valve is located over or beside the ex- 
haust valve, it should open with the crank about 5° past the 
center. If it is on the opposite side of the engine from the 
exliaust valve, it may open on the dead center, thus permit- 
ting a direct suction across the combustion chamber that will 
greatly augment the power of the engine. The inlet vslve 
should close about 20" to 30" past the dead center at the end 
of the suction stroke, or approximately 2^ to 5 per cent, of 
the piston stroke. The reason for holding open the inlet 
valve is that at high speeds the inertia of the incoming col- 
umn of the mixture will carry it into the cylinder after tbe 
return stroke has begun. 

; Iwo-l^^ 

36. The valve timing is usually adjusted by thrt 
adjusting ends on the push rods; also, by shifting the Iwo-tc 
one gear one tooth or more in relation to the pinion. If the 
total duration of opening of the exhaust valve is less than 


230°, after making due allowance for necessary clearance 
between the push rod and the valve stem, it is advisable to 
substitute new cams or else to build out the old ones. This 
can sometimes be done by dovetailing in a 
segment, as shown in Fig. 2. Generally, it 
will be necessary to anneal the cams before 
this can be done. The inserted piece is bet- 
ter located if possible in the closing face of 
the cam, as it is subjected to less wear on 
that face than on the other. It should be 
made of tool steel, and after being tightly ^®'* 

driven in and fastened with a rivet or screw, should be hard- 
ened with the cam. 

If the inlet valves are operated by the same shaft as the 
exhaust valves, it may be impracticable to alter the valve 
timing by shifting the two- to-one gears. In this case, it will 
be necessary to alter the cams. 


37. The timing of the ignition may be tested for uniform- 
ity by marking the flywheel in the same manner as for timing 

the valves. In case it is found 
that the cylinders are unequal- 
ly timed, the timer should be 
adjusted according to its con- 
struction. If the timer has a 
cam that presses springs in 
contact with contact screws, 
the timing may be modified 
by adjusting the contact screws 
so that a little more or less 
movement of the cam is re- 
P^o-* quired to produce contact. If 

the timer has a fiber barrel a with an inlaid copper or brass 
segment ^, as shown in Fig. 3, the only way the timing can 
become incorrect is through wear of the hardened-steel 
blocks r, r, at the ends of the contact brushes, or through 



loosening and slipping of these brushes, which are general!; 
slightly adjustable on their insulated bases d^ d. 

When these blocks have worn down considerably, it is wel 
to grind away a portion of their contact surface at the beai 
ing edge, as seen in the detail at e^ otherwise, considerable^ 
pressure will be required to make good contact at the leading ^^% 
edge / and this will wear away the barrel and metal sej 
ment unnecessarily fast When the timing is tested, the spar- 
should always be retarded to its fullest extent, and in th:^ 
position the spark should occur in each cylinder exactly o« 
or a definite number of degrees after, the crank has passe^^i^ed 
the dead center 


38. On account of the inertia of an exhaust valve of an 
engine running at high speed, the springs that close m^he 
valve must be very stiff, and it is sometimes a problem to 
get them back in place after they have once been taken -^out 
— as, for example, to regrind the valve. 

To replace the spring, it must first be compressed i:i3 a 
\4se and bound securely on opposite sides by two pieces 
of annealed wire. When this is done, the spring ma)'^ be 
put back in place, the valve dropped in, and the washer 
and key properly inserted. Then the wires binding the 
spring may be cut with a pair of pliers and the spring 
allowed to expand. The spring should bear squarely on \ht 

In a few engines, no washer or key is used, but the lower 
end of the spring itself is bent inwards and flattened to go 
in a slot in the valve stem. In this case, the spring may be 
taken out from the valve stem by first blocking up the 
spring in the same manner as is. done when the washer is • 
used, and the spring may be replaced by compressing an^ 
binding it as just described, holding the valve in the proper 
angular position with a screwdriver, while the end of the 
spring is first pulled and then pushed into position with a 
strong pair of pliers. 




39. Valve-stem keys should be made of annealed tool 
^teel, and should not be made too close a fit in the valve-stem 
^lot, because they are likely to bend slightly in use. Ordi- 
narily it is cheaper to buy these keys of the maker of the 
c:ar than to make them specially. One or two spare keys 
should always be carried. 


40. In case it becomes necessary to replace the piston 
Tings or to scrape out the combustion chamber, it is neces- 
sary to take off the cylinder. If the engine has more than 
one cylinder, the cylinders are probably marked to identify 
them severally for replacement. These marks should 
be looked for, and, if not found, marks should be put 
on. When the cylinders are off, care sliould be used to 
avoid handling the pistons in such a manner as might break 
their lower edges, which are very thin. When the cylinder 
is off, it is a good plan to inspect carefully the surface of the 
cylinder wall and the piston and ring surfaces, to see if they 
have been scored by lack of oil or water. The cylinders and 
pistons of a well-kept engine will show a bright, almost 
mirror-like surface, free from scratches. 

4:1. If the piston rings are clogged w^th carbon, it is, on 
the whole, better to clean them as well as possible with ker- 
osene, while in position, rather than to take them off, as the 
bending of the rings is liable to strain them out of true, 
a.nd cause leakage when they are replaced. In case it seems 
advisable to take off the rings, each ring should be marked 
with a small, sharp prick-punch, and the corresponding 
^oove marked, so that each ring will be restored to its own 
^oove. To take off the rings properly and without risk of 
straining requires considerable care. A good method is to 
use three or four narrow strips of tin or thin brass, which 
first slipped under the ends of the ring nearest the head. 


and gradually worked around until the ring* is out of its 
groove. The same strips are used to bridge the grooves 
when the other rings are taken out. 

When a cylinder is to be replaced, the piston rings must 
be compressed and tied, else it will be a difficult matter to 
get the piston into the cylinder. As each ring is started in 
the cylinder, its binding is removed. 


43. A refractory deposit of carbon in the combustion 

chamber may be loosened with kerosene and scraped out 
with anything convenient, such as a cold chisel or an old file 
with the end ground sharp. If it is inconvenient to take off 
the cylinder, it is frequently possible to remove or reach the 
carbon through the spark plug or valve holes, the scrapers 
for this purpose being generally iron rods with the ends 
flattened and bent to suit the conditions to be met An 
exceedingly useful outfit is a battery lamp of 2 or 3 candle- 
power, with a length of No. 16 lamp cord, by which it may 
be connected to the battery, and an ordinary plain (not mag- 
nifying) dentist's mirror. The lamp is screwed into a min- 
iature socket, and a length of iron wire is wound into a coil 
around the cord adjacent to the socket, the coil being 
extended to include the socket and the lamp, thereby forming 
a protective cage for the latter. It must, however, not 
touch the lamp. 

43. By the use of such a lamp, almost every inch of the 
combustion chamber of an ordinary engine can be explored 
and scraped, and the carbon can be pulled out through the 
spark-plug hole; or, if more convenient, the exhaust valve 
may be opened and the accumulation allowed to fall into 
the exhaust port, from which it will be carried to the muf- 
fler. It is better, however, to take the exhaust valve right 
out than simply to open it by the cam, as only in this way 
can one be sure that none of the carbon lodges between the 
valve and its seat, thus necessitating regrinding. When the 


carbon h scraped out in this manner, it is better not to use 
kerosene unless it is necessary, as it increases the likelihood 

of loose carbon fragments sticking to the combustion cham- 
r walls and causing further trouble from prei^tioo. 



44. Assembly drawings, showing the Icx^ation of the 
engine and some of the auxiliaries, are presented in Figs. 4 and 
5, the same letters of reference being used to indicate simi- 
lar parts of both illustrations, which serve to show one of 
many possible schemes of arrangement. The air-cooled cyl- 
inders a are bolted to a closed crank-case b^ supported, as 
shown, by two angle-iron cross-members of the frame on 
which the body of the car rests. Air is supplied to the car- 
bureter c through the intake pipe d ; while from the carbu- 
reter, the charge passes through the pipe e to the supply- 
pipe for the four cylinders. Protection against accidental 
injury to the secondary cables is afforded by a fiber tube/ 
from openings in which the cables are led to the spark 
plugs g. 

The governor on the cam-shaft is enclosed by the casing A, 
in front of which the spark timer i is located. The rock- 
shaft /, Fig. 4, controlling the spark time, is operated by the 
lever j\^ Fig. 5, connection between the spark lever under 
the steering wheel and the rock-shaft/ being made by the 
rods k and /. • Adjustment of the proportions of the explos- 
ive mixture is effected by the rod w, operated by hand. 
The steering column is shown at n. The exhaust valve o 
and the inlet valve /, as well as auxiliary exhaust valves not 
shown, are mechanically operated by push rods actuated by 
cams mounted on a single cam-shaft. The auxiliary and 
main exhaust pipes are shown at q and ^„ respectively. 

A pulley r for operating a mechanical oiling device is 
mounted on the end of the cam-shaft, as shown. A rod s, 
Fi^. 4, operated by the throttle lever /, Fig. 6, controls the 
position of the throttle. The circulation of air over the 
cylinders is assisted by the use of fan «, Fig. 5. The coil 
box V and the mechanical oiler li) are mounted on the dash, 
as shown in Fig. 5, the batter}' boxes x. x, being carried on 
the steps. The transmission gearing is enclosed in the cas- 
inir i\ outside of which is located a brake ::. 




45. In cold weather, the circulating water, the oil, and 
the carbureter, require special attention. If the car is to be 
run regularly during the winter, it is advisable to use a non- 
freezing mixture in the water-jacket. If the car is not to 
be used regularly, it may not be necessary to employ such a 
mixture, but in that case great care is necessary to prevent 
the water from freezing unexpectedly. If the car is kept in 
a barn, the water should be drawn off completely after the 
car has been used, and the drainage cock should be so located 
and the piping so arranged that there are no water pockets 
in which the water may freeze and obstruct the circulation. 
If the water freezes in the pump, the latter is likely to be 
broken when the car is started the next morning. If water 
freezes in the water-jackets, it will burst the jackets unless 
they are made of copper. When the car is left standing 
for an hour or so, cloths or lap robes may be thrown over 
the radiator to check the cooling; this is cheaper and safer 
than leaving the motor running. 

46. The two substances most used to prevent freezing 
are glycerine and calcium chloride. A 30-per-cent. solution 
of glycerine in water freezes at 21° F. ; and a solution of one 
part of glycerine to two parts of water is safe from freezing 
at 10° or 15° F. ; 40-per-cent. solution freezes at zero. A 
small amount of slaked lime should be added to neutralize 
any acidity in the solution. Glycerine has the objection 
that it destroys rubber, and the solution fouls rather quickly. 

A cheaper mixture, and one preferable where the tempera- 
tures encountered are likely to be below 15° or 20° P., is a 
solution of calcium chloride. This must be carefully dis- 
tinguished from cJdoridc of lime (bleaching powder), which 
is injurious to metal surfaces. Calcium chloride costs about 
8 cents a pound in bulk, and does not materially affect 


^^tals except zinc. A saturated solution is first made by 
adding about 15 pounds of the chloride to 1 gallon of water, 
^^king a total of about 2 gallons. Some undissolved 
^^stals should remain at the bottom as evidence that the 
^lution is saturated. To this solution is added from 2 to 3 
Salons of water, the former making what is called a 50-per • 
^nt solution. A little lime is added to neutralize acidity. 
A. 50-per-cent solution freezes at — 15® F. 

47. Whether glycerine or calcium chloride is used, loss 
^y evaporation should be made up by adding pure water, 
^nd loss through leakage by adding fresh solution. In using 
tihe chloride, it is important to prevent the solution from 
Approaching the point of saturation, as the chloride will then 
c^rystallize out and clog the radiator, besides boiling, and fail- 
ing to cool the motor. A 50-per-cent. solution has a specific 
^^vity of 1.21, and should be tested occasionally by means 
of a storage-battery hydrometer. Equally important is it to 
prevent the water from approaching the boiling point, what- 
ever the density, as boiling liberates free hydrochloric acid, 
which at once attacks the metal of the radiator and cylinders. 

A solution of two parts of glycerine, one part of water, 
and one part of wood alcohol has been recommended, which 
is said to withstand about zero temperature. 


48. Certain mineral oils used for the lubrication of refrig- 
erating machinery are recommended for cooling, because 
they remain liquid at very low temperatures. They are not 
particularly good heat conductors, however, and will not 
keep the motor as cool as the water solution. If the oil is 
used, it must be cleaned from the radiator by the use of kero- 
sene and oil soap, before water can again be used effectively. 

49. As regards lubrication, the principal danger is that 
the oil will thicken from the cold so that it will refuse to 
feed. This is avoided by using cold test oily which remains 
liquid at lower temperatures than ordinary oil, or by adding 
to the ordinary oil some kerosene or gasoline, and increasing 
the teed. It the oil tank is located close to the engine, it 


will remain warm even in quite cold weather; but, unle 
the car has been kept in a warm place over night, the bea- 
ings are liable to run dry before the car has warmed up. 

50. The temperature has a very marked effect on tK 
rapidity with which gasoline vaporizes, and in cold weatlL* 
it is necessary to supply heat to the carbureter. The ca^ 
bureter should preferably be jacketed, and it may T 
warmed either from the circulating water or by takings 
small quantity of the hot gases from the exhaust pipe, 
water is used, it should be taken from a point just beyond tl 
discharge of the pump, and should be delivered to the retix: 
pipe from the engine jacket to the radiator. Whetfci 
exhaust gases or water is used, the flow should be regulate 
by a cock, otherwise too much heat will be received in wJLir 

When the carbureter is cold, the engine may be starte 
by pouring warm water over it, care being taken not to le 
the water get into the gasoline through any aperture in th 
top; or cloths may be wrung out in hot water and wrappe* 
around the carbureter. Fire of any sort should never b 


61. The user of gasoline should never forget that it is j 
the liquid gasoline, nor yet the vapor of gasoline, tha' 
explosive, but only the mixture of gasoline vapor and ai 
the right proportions. If the liquid gasoline were nc 
volatile, it would be as safe to handle as kerosene, in v 
one may plunge a lighted match without igniting it, ther 
instead being extinguished by the cold oil. But since ga 
evaporates rapidly when exposed to the air, it is not e 
to avoid bringing a lighted match, a flame, or an e 
spark within the vicinity of the liquid — as, for examph 
gasoline has been spilled on the floor or on the groui 
one must also avoid any possible source of ignition ai 
in the neigh borhoc^ until the air has changed suffic 
dilute the vapor below the point of inflammability. 


*1 the accidents due to the handling of gasoline arise simply 
ro?ii carelessness in neglecting these precautiona 

Air saturated with the vapor of gasoline will bum 
^allowed to come in contact with fresh air, but it will not 
xplode, as the proportion of gasoline vapor in it is too great- 
t follows that a can or tank containing gasoline is safe from 
xplosion if the vapor of the liquid is saturated, and this is 
he condition that will naturally obtain if the liquid has been 
Irawn off so gradually that its place has been filled with air 
in.d saturated vapor. If, on the other hand, the can or tank 
las been emptied quickly, air will enter it to take the place of 
-he liquid poured out, and the proportion of vapor will not be 
sufficient to prevent it from being explosive. This is the 
most dangerous condition possible, and calls for the strictest 
precautions to prevent the ignition of the mixture therein. 

1«»— 17 




' ' I 





X. An installation diagram such as is shown in Fig. 1 
^^*Ves the double purpose of guide and working plan, indica- 
^'^^gf the position of the engine and showing the location and 
^^^^ngement of the accessory apparatus forming part of the 
P^'W'er equipment 

-A^inong those parts to which subsequent reference will be 

^*^^^e in the text are the shaft log a^ stern post b^ dead 

^^^^>d Cy compression coupling //, sea cock r, muffler /, and 

^^^^c^line-supply tank g. Other parts to which no specific 

'^^^rence will subsequently be made are as follows: engine 

^^lisust pipe h leading from the engine to the muffler /"and 

^^^^xiected up by means of two unions /, / and an elbow, a 

f^^'tciocky being located at the lowest point in the pipe; bat- 

^^^"3^ * and spark coil /, Fig. 1 {b) ; outboard gasoline-supply 

^I^^ w, Fig. 1 (a), from supply tank g to carbureter 7i, 

.^^T- 1 (^); reverse rod o for forward, or bow, control, con* 

^^^^ng- of a galvanized -iron pipe with ends shaped for 

^^■^Hection to the reverse-sfear mechanism and to the lower 

I ^^ of the reverse lever, which is held in the bracket/, the 

, ^^^r q being the regular reverse lever, which for use in the 

^^ of the boat can be removed from its usual position at q' 

^Ixe gear-case r; air pipe s leading to the whistle tank /, 

hf hUemoHonai Textbook Company. Entered at Stationers? Hall^ London, 



to which the signal whistle is attached; brass strainer u 
the outlet pipe in the gasoline tank; hand wheel v f 
operating the valve in the gasoline-supply pipe; and br; 
tank plate w, provided with two small vent holes. 

To install a marine gasoline engine so as to insure maxi< 
mum safety and freedom from excessive vibration necessi* 
tates a thorough understanding of all the requirements 
be met, including the construction and location of the fue 
tanks, engine, carbureter, piping, etc. , and also a thoroug! 
knowledge of the operation of the engine. Before an 
attempt is made to install the engine, there should be pro- ^ 
vided a working blueprint or drawing, indicating the dis- 
tance from the center line of the crank-shaft of the engine 
to the under side of the bed or lugs, giving all the dimen- 
sions and showing plainly the outline of the base below the 
bearing side of the lugs. A drawing of the longitudinal 
and athwartship, or crosswise, pieces, with the dimensions 
plainly marked, should accompany the drawing of the engine 

2. When the boat is new, the shaft hole is usually bored 
before the shaft log a and the stem post ^, Fig. 1 (tf), are 
put in place; if, however, it is necessary to bore the shaft-] 
hole, the work should be intrusted to some one of experi- 
ence, as it sometimes becomes necessary to make important 
changes in order not to weaken the boat or render it unsafe. 

If the shaft hole has been bored, a line should be run 
from the center of the outboard, or outer, end, in the 
direction to be occupied by the center of the propeller shaft, 
to a point considerably beyond where the front of the 
engine will come. From this line, measurements should 
then be made to determine whether or not there is suflScient 
room for the engine, reversing gear, flywheel, eta To 
obviate any chance of error, the measurements on the dia- 
gram or drawing should be verified by measuring the 
engine, so that, when once in place, the engine need not be . 
removed. There is usually a keelson a, Fig. 2, a timber , 
nmning the whole length of the boat and fastened to the 

1 1 1. 

. .OKK 



keel b over the ribs c^ Figs. 2 and 3. For the purpose of 
strengthening and stiflfening the frame, the ribs are also 
frequently fastened to similar pieces, called bilge keelsons^ 

running lengthwise of the boat. If hauled out of the water, 
the boat should now be leveled up. A plumb-bob dropped 
from the above-mentioned line at its forward end should 
mark the center line of the ke6l or of the dead wood c, 

3. Transverse pieces of oak rf. Fig. 2, of sufficient thick- 
ness should be let down to the planking e^ fitting closely 
over the keelson, and securely bolted into or through the 
keel and fastened to the planking and to the timbers, as 
shown in Fig. 2, which serves to illustrate one method of 
placing engine-foundation timbers. The timbers //, when 
fitted to the bottom of the boat and securely fastened to the 
planking, sometimes serve to form bulkheads, or partitions, 
extending all the way across the boat. Figs. 2 and 3 
show the transverse pieces let down between two tim- 
bers^ y running fore and aft, or lengthwise, and serving as 
the foundation through which the stresses set up by the 
engine are distributed throughout the whole bottom surface 
of the boat, thus lessening the vibration. 

At the lowest points on both sides of the keelson, limber s, 
or small spaces between the planking and ribs, should be 
cut to allow water to pass through ; or some means should 
be provided to pump out from each compartment separately 
any water that may collect there. When the latter and the 
safer method is employed the bulkheads should be made 


water-tight, the lower edges being bedded in red-lead or 
white-lead putty. 

If there are two or more compartments under the engine, 
they should be connected so that drippings of oil from the 
engine and gasoline from possible leaks at the carbureter 
may collect there, to be pumped out by hand or with a 
pump operated by the engine. This method of disposing of 

I ft I I I 


drippings is better than having no drip pan under the 
engine, and in a cabin boat should always be used eveft with 
a drip pan under the engine; otherwise, an accumulation of 
gas in the cabin space is liable to be ignited andlo explode 
with grave resnlts. 

With a twin-screw installation using two separate engines, 
the longitudinal timbers on which the engines rest may be 


let down a little way into the bulkheads and cut away 
slightly, so that the bulkheads themselves may securely 
support the longitudinals, which may have to be cut away or 
entirely cut off to allow room for the flywheel, but the 
longer they are the better. Almost any hard wood will do, 
but nothing is better than good sound oak. 

4t» The size of lumber used in engine beds depends 
entirely on the engine. The ordinary single-cylinder 
engine requires a heavier bed than almost any other, except 
a two-cylinder, four-cycle engine with cranks 180° apart. 
Sometimes, single-cylinder engines are constructed with 
what are known as couuterwelgrlits attached to the crank- 
shaft on the side opposite to the crankpin or to the flywheel 
in a similar position, the object being to balance the weight 
of the piston, crank, and connecting-rod. When balance 
weights are employed, it is not necessary that the bed con- 
struction should be quite so heavy. With four-cycle 
engines, even with counterweights, beds should be more 
substantial than for two-cycle engines, as the explosions do 
not occur so often, and, being more powerful, are more 
likely to cause excessive vibration. 

Double-cylinder four-cycle engines with cranks opposite, 
or 180° apart, require an engine bed of the heaviest con- 
struction, because there are two impulses during one 
complete revolution of the crank-shaft, the explosion in the 
second cylinder following closely upon that in the first, 
accelerating the crank-shaft speed ; a complete idle revolu- 
tion follows; the latter half of the revolution, being against 
the compression, causes a particularly unpleasant vibration 
that, unless absorbed by the engine bed or the boat itself, 
may be unsafe because of the light construction of the boat 
or the presence of some defect. Two-cycle engines of twp 
or more cylinders and four-cycle engines of thr^e or more 
cylinders are better balanced and do not require such heavy 

5. In some cases, it has been found necessary to put in 
braces from the top of the engine to the side of the boat, the 


engine bed and lower part of the hull being too light. It is 
customary to make the hull where the engine is to be 
placed of much heavier construction by putting in a double 
framing of extra or heavier ribs. Weak engine beds may 
sometimes be strengthened materially by filling in about 
the timbers with Portland cement and sharp sand. 

It is rarely found necessary and is hardly advisable to fasten 
engine beds through the ribs and planking, as is often done 
in marine steam-engine, practice, for such fastening tends to 
weaken the hull construction instead of strengthening it. 

A drip pan of good depth under the engine is necessary 
for catching all dripping oil, and, if connected to another 
pan under the carbureter, gasoline that may leak there will 
be prevented from getting into the hull of the boat, running 
into the drip pan instead, from which place it may readily 
be pumped out This drip pan should be fitted under the 
base of the engine and to the hull before the engine is in 
place. The edges should be flanged over the longitudinal 
pieces of the engine bed, which should be cut away so that 
the engine base will not bear on the edges of the drip pan. 
Copper makes the best material for a drip pan, but galvan- 
ized iron may be used in fresh water only, the outside of 
the tank being well protected with asphaltum varnish, 

6. Before placing the engine on the bed, be sure that 
the two longitudinal timbers are not in wind, that is, with 
the end of one higher than the same end of the other. This 
would make the engine rest like a four-legged chair with 
one short leg. To determine whether or not there is 
wind to the bed, place a level squarely across both forward 
and after ends, or build up the after ends alike until they 
are both level, and see whether or not both longitudinal 
pieces are true. A little variation from a true level wnll 
make quite a difference in the character of the stresses set 
up when the engine is in place and operating. It may be 
necessary to cut away a part of one or more of the bulk- 
heads to make room for the base or reversing gear. 

If, ha\nng the en.crine on the bed, the engine base is 


continued to support the reverse gear r, Fig. 1, put in the 
propeller shaft, put on the stuffingbox and separate stem 
bearing if one is used, and, if the propeller shaft is to be 
coupled by means of a sleeve coupling, see that the ends of 
the shaft project into each end half way, with the key 
removed, and that the propeller shaft turns freely. If a 
compression coupling d^ Fig. 1, is used, see that both shafts 
are in line. If the two shafts are flanged, see that they 
come fairly together, moving the engine slightly, if neces- 
sary, in order to get the shafts absolutely in line, and block- 
ing up the forward or after end of the engine, if necessary, 
being particular that the propeller shaft does not touch the 
side of the lead sleeve in the shaft log a, Fig. 1. If a brass 
sleeve is used, it should not be fastened until the engine is 
lined up, as stern bearings and stuffingboxes are usually 
screwed into the brass sleeve. Lead sleeves are usually 
considerably larger than the shaft ; their ends are flanged 
over and copper- nailed, after being bedded in putty consist- 
ing of white lead stiffened to the proper consistency with 
red lead. Where no sleeves at all or lead sleeves are used, 
stem bearings and stuffingboxes should be fastened flush 
with the ends of the shaft log, by means of bronze screws 


Fig. 4 

when the stuffingboxes and stem bearings are of bronze, 
and by means of iron or steel screws when iron stem bear- 
ings are to be used. Iron or steel stem bearings should 
never be used around salt water, except with very large 
shafts, lignum-vitae bushed stem bearings and bronze 
bushings always being used on steel shafts. While bronze 
lag or coach screws as sent out from the factories are usually 
employed, a much better custom is to use bronze studs with 
a wood-screw thread on one end and a bolt thread on the 
other, as in Fig. 4. These studs can be screwed into place 
by screwing on a nut half its thickness and screwing 


another stud down hard against the firat, as in Fig. 5. A 
stud driver Fig. 6 may also be used. This consists of a 
square or hexagooai piece of metal a, threaded as shown to 
receive the machine- screw end of the stud 6, which is locked 
in place by the capscrew c while the wood-screw end is 
being screwed into place. One special precaution to be 

observed in fastening all stem bearings and stuflBngboxes is 
to see that they rest squarely against the wood and that a 
thin layer of red-lead putty is placed between the metal and 
the wood, the metal being drawn into place so that it does 
not bind the shaft 

7. Small engines are usually fastened to their beds by 
iron screws, but a more satisfactory fastening will be found 
in steel or iron studs, similar to the bronze ones used- fw 
fastening the stem bearing and stiifEngbox. In case of 
necessity, it will be found much easier to remove a few 
nuts than to remove the coach screws, especially after they 
have been in place a year or so. Wlien it becomes neces- 
sary to line up an engine with a separate reversing gear, the 
shaft of the latter should be sufficiently long to extend from 
the after bearings to the crank-shaft. After lining up the > 
crank and propeller shafts, a temporary bearing should be 
erected abaft the reversing gear, which is usually supported 
with a thrust, the gear shaft then being lined up with the 
crank and propeller shafts and securely fastened. 

If it is found necessary to raise either end or side of the 
engine to line it with the shaft, thin pieces of iron or tin 
will be found very convenient, or thin pieces of hard wood 
may be used. 

8. In case the flywheel is shipped separately, or lias to 
be removed to get the engfine into place, it should, if bond : 


Straight and the key driven in, be replaced carefully in 
exactly the right position, noting that the key rubs on all 
four sides by taking it out two or three times after starting 
to see that it fits. If the flywheel is fitted on a taper, as is 
sometimes the case, care should be exercised that the key 
does not prevent the wheel from going into its proper posi- 
tion on the shaft because of its being too thick or being 
placed wrong side up. Flywheel keys should always fit on 
both sides as well as top and bottom, and should be oiled 
before being driven into place. Occasionally, a flywheel and 
a crank-shaft are found in which the keyways are cut a V 
shape and extreme care should be used in driving in the key, 
for there is great liability of splitting the hub of the fly- 

The fastening of flywheels securely to the crank-shaft 
is such an important matter that some manufacturers make 
the crank-shafts with a flange on the flywheel end, the flange 
being bolted to a web in the flywheel. 

9. In some cases it will be found necessary to take the 
engine apart more or less to get it through a companionway 
or skylight. If the operator or other person making the 
installation has had much experience with machinery, he 
will observe much caution in taking it apart, marking each 
piece, usually with a center punch, so that each gear will 
mesh with the same teeth when putting together again, and 
each part will go back to its proper place. For thus marking 
the parts, a center punch and a light hammer will be found 

10. The alinement of the engine and propeller shafts is 
an important proceeding, more particularly if no universal 
coupling is used. In extremely light boats, as in yacht 
tenders, and when using engines designed to be installed 
level or more nearly level than the propeller shafts, universal 
couplings are necessary. They are of numerous forms and of 
varying utility; the greater the angle between the two shafts 
thus connected, the more unsatisfactory is their use. While 
the engine and propeller shafts are being lined up, the boat 




should be blocked up evenly along her keeL No matter how 
carefully the work of lining the shafts may be done, it will 
be necessary to reline them after the boat has been put in 
the water and has assumed her normal shape. When the 
engine shaft is in line with the propeller shaft and the stem 
bearing and stuffingbox are securely fastened, the engine 
should be fastened to the bed, after which the water and 
exhaust piping may receive attention. 



11. In piping up for the circulating water, care should 
be exercised that leaks do not develop at the sea cock (, 
Fig. 1 (a)^ where the water from the outside enters the boat 
The usual method of making the sea-cock connection is to 
use a long brass nipple, \\\\h a locknut outside and inside, and 
with washers underneath. In some cases, the water connec- 
tion is arranged as shown in Fig. 7; it is put through fro"^ 
the outside of the plank, with a brass washer a under tt*-® 


Fig. r 

sluMiKlor »*, tV.o whole being held in place by a brass locknu 
\\'.:> Wvw.en \v.i>heis ur.deriiea::: it. The water piping 
\\w\ Svvcwed iv^ r::c er.vl. A ir.uch safer method c 

>s:^ o! r*.::":'.j^ tv^ :;'.o i:isiJ.o v :" I'/.o rl.irkir.gablockof wood V 

vv : »reo :'"!*o> .;< 

v. N 

.\< :Vo r'.r.k rv:. The buxrk is bedd 


in putty, and is then carefully and solidly fastened to the 
planking. A hole just large enough to admit of passing 
through it a piece of lead pipe of good thickness, and having 
a clear way fully as large as the inside of the pipe to be used 
for the water suction, is then bored through the block and 
planking. The hole should be chamfered outside and inside. 
One end of the lead pipe should be flanged out and ham- 
mered into the chamfered edge at the inner end of the hole 
in the pipe, being cut off about ^ inch beyond the outer end 
of the hole. Then holding in place the inner end, the outer 
end should be flanged over and nailed with copper nails 
spaced rather closely, being sure to have white or red lead 
under the flanges. A brass railing flange can now be 
screwed to the end of a short annealed-brass nipple, which 

had better be soldered in to obviate danger of unscrewing in 
case it should ever be necessary to remove the piping, stop- 
cock, or valve attached to this nipple. The flange should 
then be bolted against the inside end of the lead pipe, as 
shown in Fig. 8, using button-head brass bolts, which 
pass through the outside planking. If long brass wood 
screws are used, they should be cut off outside the planking. 
The piping should be led to the pump suction, using two or 
three regular or ib" elbows, and a sufficient length of piping 


and number of fittings to take up vibration without causing 
leaks or other injury to the planking. Rubber hose is some- 
times used; but, unless the piping is led to a point higher 
than the water-line, and kept above it, a leak might fill the 
boat with water. 

Whether a reciprocating or rotary pump is used, there 
should always be a check- valve close to the suction end of 
the pump to keep water in the pump and engine cylinders 
when the engine is not running; otherwise it would be 
necessary to prime the pump when starting, and the cylin- 
ders would remain hot for a long time after stopping. For 
use in cold weather, it is necessary that means be provided 
for draining the water piping to prevent freezing of the 
water and consequent injury to the piping and water-jacket 
The piping between the pump and the engine is usually pro- 
vided and put in place by the manufacturer, but if no means 
of draining it is provided drip cocks shotdd be put in. 

Outside the hull, where the circulating water is taken in 
through the sea cock, there should be a flat copper or brass 
strainer to prevent grass or other foreign matter from being 
drawn into the pump or from stopping the action of the 
check-valves. The holes in -the strainer should be fairly 
close together, and about ^ inch in diameter. The metal 
should be fairly heavy, and the strainer should be securely 
fastened to the hull by means of small brass screws. 

13. The discharge water piping in a multicylinder engine 
should always lead from the highest part of the engine, that 
is, from the forward instead of the after cylinder. In order 
to avoid danger of bursting the cylinder, no valve should ever 
be placed in the discharge piping. The best method is to 
branch the discharge, running one pipe into the engine exhaust 
pipe and the other outboard, the outboard branch being pro- 
vided with a square-headed cock. As there is always a cer- 
tain amount of pressure in the engine exhaust pipe, the dis- 
charge water would naturally flow more freely through the out- 
board branch and cock; but a part of the discharge watermay 
readily be diverted to the engine exhaust from the outboard 


discharge pipe by partly closing the cock. If conditions were 
such that too much water was diverted to the engine exhaust, 
and if it were found impossible to reduce the amount of 
water by means of the cock in the outboard discharge branch, 
the cock should be placed in the branch to the engine 
exhaust, being removed from the outboard discharge, lest by 
any chance both discharges shoijld be closed, in which case 
the pressure created by the water pump might burst the 

13. When it is necessary to install an engine with the 
top of the cylinder lower than the water outside the boat, 
extreme care should be exercised that the discharge water 
does not get back into the cylinder through the engine 
exhaust by way of the exhaust valves or ports. One of the 
best methods is to water-jacket the engine exhaust pipe, the 
water-jacketing pipe being led outboard or run to the muf- 
fler or to the highest part of the exhaust piping where the 
water cannot run back to the engine. Under no conditions 
should engines constructed so that a part or all of the jacket 
water is discharged around the engine exhaust be installed 
with the top of the cylinder below the water-line, unless 
some means is devised to prevent the water discharged into 
the jacket about the exhaust from entering the cylinder 
through the exhaust pipe. The water from the cylinder 
head is sometimes discharged into a space about the muffler, 
the water entering the exhaust piping when it reaches a cer- 
tain height 

Attempts have been made to overcome the difficulty due 
to the passage of water from the exhaust pipe to the engine 
cylinder, by placing a valve in the branch to the exhaust 
pipe, closing the valve when the engine stops and opening it 
when the engine starts. As a result of forgetting to open 
this valve, the exhaust pipe and muffler may set the boat 
afire ; and were the operator to forget to close it, the cylinders 
may fill with water. If the exhaust pipe can be run high 
enough at the engine to drain away from it, the jacket water 
may safely be discharged into it at this high point; but it is 


best not to run water into the exhaust pipe, an inside water- 
jacketed exhaust or outside cooling method being preferable. 

14. The best location for the sea cock, or water intake, 
is a few inches below the water-line, for at that point the 
cock is less liable to get clogged with sand or grass. With 
a good strainer over it, it ca^ easily be reached and cleaned. 
If, however, the boat is what is known as an auxiliary^ that 
is, a boat intended to be propelled by both sail and power, it 
is a good plan to locate the sea cock lower down, in order to 
be sure that it will always be submerged. 

In reducing the amount of water thrown by the pump, 
it is always best to throttle it at the suction, never at the 

Another thing to remember is that the water piping should 
be run so as to avoid any possibility of flooding the boat 
through siphonic action. 

1 5. For use in salt water, the piping should be of annealed 
brass, which is easier to install and safer because of freedom 
from corrosion. Sharp turns in piping are to be avoided 
where possible, and the use of 45° elbows instead of the 
regulation 90** elbows is always advisable. 

In sight, and at places handy to get at, malleable-iron 
fittings should be used ; but out of sight, and in close quar- 
ters, cast-iron fittings will be found better, because they can 
easily be broken, especially if it is ever necessary to take 
down the exhaust piping. It is always advisable to use 
plenty of graphite and cylinder oil in making up exhaust- 
pipe joints. Flanged unions will be found preferable to 
ordinary malleable-iron unions, for it will usually be found 
easier to cut off the flange bolts than to take down a screwed 
union after it has been used a season. Graphite and cylinder 
oil or graphite pipe grease will be found better than red or 
white lead in making up joints in the water piping. 

16. The engine exhaust maybe piped outboard in many 
ways, the simplest being to pipe it directly through a muflfier 



arranged vertically. While simple, this plan is not often 
adopted. A dummy stack makes an excellent place for an 
exhaust, but it would not be safe or expedient to run jacket 
water into it, because the water would run back into the 
engine. In many open launches, it is found quite conven- 
ient to exhaust through one or both sides of the boat. In 
most cases, especially in auxiliaries, the exhaust should issue 
at or above the water-line. Some boats, however, are pro- 
vided with an under- water exhaust With four-cycle engines, 
it is usually customary to vent the exhaust piping at a point 
considerably higher than tlie water-line, in order to prevent 
water from siphoning back to the engine. Siphoning is 
much more liable to take place with engines using positive 
inlet valves than with those using automatic inlet valves, 
for the reason that, when an engine of the four-cycle type 
stops, the exhaust piping, muffler, and combustion chamber 
are usually filled with hot gases and steam. These condense, 
creating a partial vacuum, and if the exhaust valve is off its 
seat, as it is on the exhaust stroke, and the inlet valve is 
held to its seat, water from the exhaust pipe is liable to be 
drawn into the cylinder or into the valve chamber, rusting 
the exhaust- valve stem and thus causing it to stick. In a 
two-cycle engine siphoning would not be so likely to occur, 
because as the hot gases and steam condense and the exhaust 
port is open, the passover port also would be open, thus 
relieving the vacuum. 

Mufflers should be piped so that the exhaust enters the 
npper side or upper part of the end, leaving at the lower 
end, and draining outboard, as shown at_/, Fig. 1. 

1 7. One of the chief dangers from fire in boats propelled 
by gasoline engines, whose exhaust piping is not water- 
cooled, is from overheated exhausts. These fires are eaaly 
discovered, and if the gasoline tanks are not located near the 
exhaust piping, there is very little danger of burning up the 
boat- In all cases the exhaust piping and muffler, unless 
cooled, should be protected with sheets of asbestos board 
securely bound on with wires or metal straps or some 



similar pipe covering. The exhaust pipe should extend | 
inch or more through the planking, to prevent iron rust or 
soot from staining the paint. 


18. The safest location for the gasoline tank g^ Fig. 1, is 
in the bow of the boat in a water-tight compartment. Some 
manufacturers make a practice of using a drip pan of liberal 
height under the tank, connecting the two lower after comers 
with the outside by means of scuppers or openings through 
which it may drain when the drip pan is located above the 
water-line; otherwise, means are provided for pumping 
accumulations of water or gasoline from the water-tight com- 
partment. Some objection may be made that the differ- 
ence in weight of a full or empty tank affects the trim of 
the boat, but this objection is trivial compared with the 
advantage of safety. When tanks cannot be placed in the 
bow, it is allowable to locate them on deck or in the cockpit, 
in the open place in the stem, or under the seats. In both of 
the last two places, the drip- pan system with outboard drain- 
age should always be employed. 

19. The material from which tanks are made differs 
with their capacity. Tanks up to 40 or 50 gallons, made to 

fit the contour of the boat and located 
in the bow, or under the seats in the 
cockpit, should be constructed of hot- 
rolled or soft-rolled copper tinned on 
the inside. For the larger sizes, no less 
thickness than that weighing from 30 
to 36 ounces to the square foot should 
be employed; while for smaller sizes 
of from 10 to 15 gallons capacity, 24- 
ounce copper should be the lightest 
^^°-^ allowable. The tanks should he 

double-seamed, as shown at a. Fig. 9, on all edges except 
the top, which may be a single seam, as shown at ^, both 


seams being carefully soldered. Longitudinal and trans- 
verse partitions, or svrasli plates, should be provided, so 
that there may be in the tank no spaces larger than 12 
inches in either length or width. Thus, for a tank 18 inches 
wide and 4 feet 3 inches long, there should be one longitud- 
inal and four transverse partitions. 

The object of these partitions or swash plates is to prevent 
the contents of the tank from rushing from end to end of the 
tank and also to support, or stay, the sides and bottom. An 
unobstructed movement or swashing of the gasoline would 
be liable to dislocate the tank, break the gasoline piping or 
tank connections, or stir up water or sediment that might 
be present in the tank and cause a clogging of the car- 
bureter or vaporizer. Even though the longitudinal parti- 
tions may sometimes be omitted the transverse plates should 
not be left out under any pretext. They should be riveted 
to the bottom and sides of the tank, and, to prevent electro- 
lysis in case salt water should ever be present, should be of 
the same material as the remainder of the tank. Apertures 
should be cut at the bottom to allow a free passage of the 
contents from one compartment to another. The top of the 
tank should be crowned slightly to prevent thy accumula- 
tion of gasoline or water. 

20. Before the top is put on, the connections should be 
made for the gasoline supply and drain to the tank. Where 
these connections are to be made, the sides should be rein- 
forced by copper of the same thickness as the tank, project- 
ing several inches above and to each side. These reinforcing 
pieces should be riveted and soldered or sweated to the side 
or the end of the tank rather than to the bottom. The supply- 
pipe connection should be 2 or 3 inches higher than the drain- 
pipe connection. The supply -pipe connection should be of not 
less than j-inch iron-pipe size, seamless, soft-copper or brass 
pipe, with two locknuts and washers — one nut and washer 
on the inside and another on the outside — the whole 
being sweated together with soft solder. The object of 
thus soldering the connections is to prevent loosening 


them in connecting or disconnecting the valve or supply 

21, The gasoline tank and the drip pan should be con- 
nected together rigidly, so that the tank will not slide around 
in the drip pan. The supply pipe should pass through a stuf- 
fingbox either at the top or at the bottom of the side of the 
drip pan. There should also be a stufEngbox where the sup- 
ply pipe passes through the hull in case outside piping is used, 
or through the water-tight bulkhead in case it is decided to 
use inside piping. All piping for gasoline should be of 
ample proportions, never less than \ inch, preferably f inch, 
iron-pipe size, and should be of soft, seamle;5S copper or 
annealed brass, preferably the former; under no cir- 
cumstances should lead or block-tin piping be used, because 
of liability of leaks due to breaks caused by vibration. 
With lead and tin piping there is also considerable uncer- 
tainty as to whether or not the brass nipples used are sol- 
dered properly. A screwed and soldered joint is much safer 
than a plain soldered one. 

Where the outside piping enters the boat, another stuffing- 
box or similar contrivance should be employed. The suppl 
pipe should enter as near the carbureter as practicable, an 
between the carbureter and its entrance there should 
interposed a helically wound coil to take up vibration an 
prevent stress on the piping where it enters the boat^ 
Breakage at this point is accompanied with grave danger ^ 
and on this account the piping should at all times be pro — 
tec ted against possible contact with ballast or anything liable 
to injure or rupture it. 

Stop-cocks should be placed close to the tank, and also 
between the carbureter and the point where the piping" 
enters the hull. Outside piping should be protected by ^ 
bronze shoe where it passes through the planking at the bow, 
and with a grooved piece of oak put on with brass screws 
and extending the whole length of the outside pipe. 

33. Gasoline filling pipes and vents to the tanks are 
very important features and frequently get little attention. 




If the filling pipe extends several inches into the tank, 
and small vent holes are drilled in it, as in Fig. 10, just 
below the top, when filling with a long funnel that extends 


FlO. 10 

Fio. 11 

below these holes, air from the top of the tank displaced by 
gasoline running in will escape through these small holes 
and will not cause the gasoline to slop over. The filling pipe 
may be made of lead and flanged over at the top, as in 
Fig. 11, the whole being covered by a brass deck plate, or 
cover, with screw plug. 

23. The vent at the highest point of the tank should be 
a piece of brass pipe extending into the tank several inches 
and having two small holes as in the filling pipe. To this 
pipe there should be screwed a brass T having at one end a 
short nipple and check- valve to relieve pressure in the tank, 
and at the other end another short nipple and check-valve 
to relieve the partial vacuum in the tank caused by drawing 
out the gasoline. This arrangement will be found more 
satisfactory than drilling a pinhole in the plug, or using a 
loosely fitting screw to relieve pressure or vacuum. Under 
no circumstances should pressure be applied to the tank to 
cause gasoline to run to the carbureter. 


24. It is sometimes convenient to use copper or galvan- 
ized-iron kitchen boilers instead of rectangular tanks. 
Unless they are especially made and have partitions in them, 
such boilers should be as short as possible. If they have no 
partitions, they should preferably be set on end. If they 
have to be placed in a horizonal position, they should be 
solidly and carefully blocked and secured, to prevent them 
from moving and breaking the gasoline-supply connections 
or piping. 

When large quantities of gasoline are to be carried, the 
tanks should be built like steel steam boilers, with the neces- 
sary swash plates riveted and calked, and as a f lurther pre- 
caution they should if possible be galvanized inside and out 
Cylindrical tanks are preferable to rectangular tanks, and 
should be employed where there is sufficient room. 

In case it should be necessary to locate the tank on deck, 
the inside of the wooden covering, or hatch, should be 
lined with asbestos or some other non-conductor of heat 
In any case, the same system of drip pan, vents, etc should 
be employed, except that for filling purposes a removable 
hatch may be used if desired, but care should be exercised 
in tilling the tank not to allow it to run over. 

25. If the engine is to be operated from some part of 
the boat other than at the engine, the various controlling 
devices should be attached and tested to see that they work 
properly. From whatever point the engine may be handled, 
a connection must be made so that the gasoline supply may 
tK.* shut off every time the engine is stopped. 

S 22 





26. When an engine is about to be started it is not safe 
to assume that all the adjustments are correct, just as they 
were when the engine left the shop, and only by careful 
examination can the operator be sure that the engine is 
ready for use. The following general rules may be applied 
whether the engine is of the two-cycle or the four-cycle type, 
either single cylinder or multicylinder. 

First, determine which way the engine runs normally, 
whether right-handed or left-handed. When facing the fly- 
wheel and looking toward the stem of the boat, if the direction 
of rotation of the flywheel when the boat is going ahead is 



Pig. 12 

the same as that of the hands of a watch, as shown by the 
arrow in Fig* 12 («), the engine is a right-hand engine and 
requires a left-hand propeller wheel to drive the boat ahead. 
When the movement of the flywheel is contrary to the direc- 
tion of movement of the wat^h hands, as in Fig. 12 (^), the 
engine is a left-hand engine and requires a right-hand 


propeller wheel in order to propel the boat ahead. When 
turning it over rotate the flywheel in its proper direction with 
the cocks open, or with the compression otherwise relieved. 
Determine when the piston is on the upper dead center, and 
make a mark on the flywheel in case the starting pin that 
fits into the hole «, Fig. 12 {a) and (^), is not where the mark 
would come. If there is no starting pin, or if it should be 
set at a point 90** from the upper dead center, mark the fly- 
wheel plainly to indicate when the piston is on the upper 
center, another mark being made on the opposite side of fly- 
wheel to show when the piston is exactly on the lower cen- 
ter. If the starting pin in the flywheel is set 90° from 
the upper center, its position should be changed to corre- 
spond with the mark made to show when the piston is on 
the upper center. Any other location for the starting pin is 
dangerous, giving rise to broken and sprained thumbs, wrists, 
and arms, besides other injuries. 

Having marked the flywheel to show the position of the 
piston in the cylinder, then, with the gasoline turned off 
and the battery switch closed, turn the flywheel slowly until, 
if a jump spark is used, the spark coil begins to buzz, where- 
upon another mark should be made on the flywheel. If the 
make-and-break system of ignition is employed, note where 
contact is made and where it is broken when the spark occurs. 
If the engine is of a multicylinder type, try each cylinder 
separately, to determine whether or not the contact is made 
at the same relative position for all cylinders and that the 
spark occurs at the same point before or after the center is 

37. If the engine is of the two-cycle type using jump- 
spark ignition or the usual form of make-and-break ignition, 
which will allow it to nm in either direction, turn the flywheel 
in the opposite direction until the mark shows it to be about 30° 
before the upper center. Then, advance or retard the spark 
until a contact is made just at that point, and note the p)osi- 
tion of the spark-control lever. If the engine is of the single- 
cylinder, two-cycle type, the easiest method of starting the 



33 ' 

engine is to prime the combustion chamber bj- injecting a few 
drops of gasoline into the priming cup with a squirt can, and 
turn on the gasoline supply in case a carbureter is used, prim- 
ing it also by depressing the float; if, however, a vaporizer is 
used, set the needle valve at the point usually made on the 
dial when the engine is tested, swing the flywheel several 
times slowly back and forth through a space equal to about 
one-third the circumference, and then, takingfirmholdof the 
starting pin, swing it up smartly against the compression in a 
direction opposite to its normal rotation, and then let go. 
If the engine does not start after trying this two or three 
times, first close the valve in the gasoline supply, open the 
relief cock, and turn the engine over three or four times, and 
note whether or not explosions occur. The relief cocks should 
be open and the spark lever set so that ignition will occur 
either just after the center is passed or as near the end of the 
up stroke as possible. 

88. In two-cycle engines using make-and-break ignition 
that will run in either direction, motion is given to the 
igniter or movable electrode by means of an eccentric 
securely fastened to the crank-shaft or hub of the flywheel. 
The high part of the eccentric is either in !ine with the crank- 
pin or directly opposite, usually the former. Reference to 
Fig. 13 will make it clear that the eccentric carries the rod 
that moves the igniter upwards during 
/^- — V \ one-half of the revolution of the crank- 
/ \ \ shaft and downwards during tlie other 

Y J \ half. The tripper must therefore act 

^ — -^ ] before the extreme top or bottom center 
is reached, no matter ia which direction 
the crank-shaft turns. In engines de- 
signed to run in but one direction, this 
' '"■ "* is a comparatively simple matter, for the 

eccentric can be secured bo that it will not arrive at its high- 
est point until after the upper center is passed. This is true 
also of nearly all four-cycle engines; for, unless they are 
designed to run both ways, the action of the ignition cam 


is retarded, and if designed to run both ways, separate 
cams for ignition, as well as valve operation, are always 

29. Fig. 14 shows a method of arriving at a solution of 
the problem of igniting the charge before or after the upper 
center is passed. An eccentric that is not keyed to the shaft 

Pio. 14 Fig. 16 

is provided with a pin that projects through a curved slot in 
the web of the flywheel; and, by fastening the pin to one 
side or the other of the middle of the slot, the ignition will 
be delayed or advanced when the engine is running in either 
of the directions indicated by the arrows just above the slot 
Another method employed is to have in the eccentric a 
slot wider than the key that fastens the flywheel, the key 
extending into the keyway in the eccentric, as shown in 
Fig. 15, the eccentric being mounted loosely on the flywheel 
shaft, as in Fig. 14. 

30. Fig. 16 shows a double motion used by another manu- 
facturer to obtain the same result. In this figure, a is the 
crank-shaft; *, the eccentric; r, the eccentric rod, or strap, 
pivoted at d in the slot^. The position shown would not 
allow the pin f^ which is raised by the forked end <rf the 
eccentric rod c, to trip and separate the electrodes until a 
considerable time after the center had been passed; but, if 
the eccentric h were turning in the direction indicated by 
the arrow, and tlie eccentric rcid c were held to the left, it 



would trip earlier, or at such a time in the upward motion as 
desired, this time being regfulated by the amount the rod is 
held to the left, which is controlled by means of the hand 
lever k. If the reverse motion 
is given to the eccentric, the eccen- 
tric rod would give the same time 
of ignition, provided it were held 
at the same relative position to the 
right, instead of to the left. 

31. Multicylinder two-cycle 
engines, unless they have some / 
such means as described for re- 
tarding the spark, if designed to 
run in both directions, are ex- 
tremely dangerous to start and 
very much more so if they are 
provided with a starting pin in the 
flywheel. Every owner of a mul- 
ticylinder marine engine should 
remove the starting pin, if one is 
used, just as soon as possible; if 
left in, it may cause serious injurj'. 

A multicylinder two-cycle en- 
gine should never be started in 
the same manner as is usual with 
single-cylinder two-cycle engines, nor should the attempt 
to do so ever be made. It is very important that this 
should be remembered; if any one should attempt to start 
a multi-cylinder two-cycle engine by rocking the flywheel 
back and forth, as is customary with single-cylinder two* 
cycle engines, and tliere happened to be a charge of gas 
left in any of the cylinders, the ignition of such charge 
might cause a serious accident, many persons having been 
injured in this manner. 

3S> In four-cycle engines, the une of a starting pin is 
unnecessary and even more dangerous than with two-cycle 
engines, for the result would bo just as bad if an explosion 




should take place and the engine were to start ahead as it 
would if a back kick occurred and the operator did not let 
go of the starting pin in time. . Starting pins are unneces- 
sary, engines without them being provided with flywheels 
of larger diameter so as to be more easily grasped by the 

Small sizes of four-cycle engines with flywheels on the 
forward end of the crank-shafts are usually started by grasp- 
ing the flywheel, although some are designed to use a starting 
crank that automatically releases as soon as the engine 
starts. . 

Fig. it 

33. If a starting crank is used, it is manifestly easier to 

start a marine engine that nms right-handed than one that 

runs left-handed. For this reason, nearly all 
marine engines that are crank-started, are 
right-handed. The starting crank usually 
hooks over a pin in the end of the crank-shaft, 
as in Fig. 17, or over the end of the key hold- 
ing the fl}n^-heel in place, in w^hich case a 
left-handed crank should be used to run the 

engine left-handed, or a right-handed crank to run it right- 

The pin should so engage the starting crank that the 

engine \Nnll pass the upper center at a point about 45^ before 

the starting crank reaches the center, as 

in Fig. 18. In this case, to start an engine 

lett-handcii on the compression stroke, 

the crank-handle would describe one-half '/ 

a circumterenoe. d-ti-t/^ or 1S«»^^: while, if * 

riiiht -handed, it would be ii-^'. The 

n\ovo:r.oni v>! the crank-handle should 

aiwavs Iv iii^warcs. the oh^ect beinij to 

*•/.: ;::> ^^ti the h.\r.v;'.c when the irreatest 

>.>-->-,-« -y^^ charge, and when on^^ 

.V . V V. 

V. ». 


tv^ v>"' 


:r.-y;e:e the halt-turn mov'^ 
■ :^o.v< :,:r.*::.^" is employed. Suppc:*^ 
vo 'x-or. .i.lvAr.cOvi to a point/. Fig. ^^ 


and that at this point the electrodes were in contact^ if 
the force exerted to compress the charge were removed, 
the handle might go back to, say, e^ when, M the Electrodes 
were to separate, a spark w^onld occur and a back kick 
would result. On the other hand, if the crank were to be 
carried to r, or were to pass it, the piston being thereby 
carried beyond the upper dead center, the expansion of the 
compressed charge would carry the piston part way down 
until the igniter would trip and ignite the charge, and 
motion would be given to the crank-shaft in the proper 
direction. Sometimes the crank-handle describes the half 
circle g-h-e^ or e-h-g^ but it is better and safer when the 
path of travel is a-b-c or b-a-d. No matter where the 
crank-handle path is located, if for any reason the operator 
is tmable to get the piston past the upper center, and 
make-and-break ignition is used, there is danger of back 

34, Instead of a pin through the shaft, a ratchet wheel 
of one, two, four, or more teeth is sometimes keyed to the 
shaft. A single tooth is much safer than two or four teeth, 
more than two teeth being unnecessary as well as unsafe. 
If a two- toothed ratchet is used, the crank -handle should 
describe the arcs a-b-c or b-a-d^ also c-d-a or d-c-b. 

In three-cylinder engines having cranks set 120** apart, a 
three-toothed ratchet should be employed. If a pin is used 
in the crank-shaft, it should not extend through, as in 
Pis'- 17, but in the starting crank there should be three 
hooks 120** apart, to give the same relative motion in com- 
pressing and exploding the charge in each cylinder. 

Where the engine is too large to start by ordinary means, 
various mechanical devices are employed. Some of tliem 
are more dangerous than others, and any one of tlaem in 
the hands of an inexperienced person may cause injury to 
the operator or others. 

35. Fig. 19 shows one meth<^ of using a starting bar. 
The flywheel for a single-, double-, or four-cylinder engine 
usually has four cored apertures, arranged 00** apart, with 



a and 6 usually 45'' ahead and back of the upper center, 
respectively, and with c and d diametrically opposite a 
and b. There are two rows of these if the engine is 
designed to be run in both directions. In right-handed 

Pio. 10 

action, the lever has a toe e that comes against the side g, 
with the heel /against A. As soon as the engine starts, the 
lever is easily withdrawn; this is, perhaps, the simplest 
starting-bar system. 

Another starting bar, the construction of which is shown in 
Fig. 20, consists of a toothed ratchet a, with a yoked bar t, 
and a pawl c engaging the teeth of the ratchet The teeth 
are usually hooked more or less, and if the engine is to be 
run in both directions, it is necessary to have two ratchets 
and one pawl, turning the forked lever half way around to 
run in the opposite direction. In this case, as in using 
starting cranks, it is necessary to see that the explosion does 
not take place too early, or it may result in injury to the 

36. Frequently, in using a crank in close quarters, it is 
customary to bend it just above the pawl, so that the handle 




will lead to a point about 45° from the crankpin. This will 

make it possible to get a hold lower down. If there are 

tnoTe than four teeth the same danger exists as in the case 

of more than two teeth to the 

starting crank. If the engine 

is not too large to start without 

relieving the compression, the 

utmost care should be exercised 

in starting the engine, and the 

use of a four-toothed ratchet 

should be discouraged. 

37* If the engine is one in 
which the compression must be 
relieved in order to start, almost 
any one with a little ingenuity can 
arrange an attachment whereby 
the compression may be relieved 
and the spark retarded at the same 
time. Fig. 21 shows how this 
may be done; ^, a\ and a" are 
three cylinders having relief cocks 
i, d\ and 6" connected through a suitable rod to a bell-crank 
lever c pivoted at d. In the position shown, the relief cocks 
are open. Suppose, now, that they are in closed position. 

Pig. 90 

Fig. 21 

as indicated in Fig. 22, and that a rod r, passing through 
a pivoted stud in the spark lever, is provided with collars / 
and £" held in place by setscrews or other means, the rod e 


sliding through the guide i until the relief cocks are open, or 
nearly so, before the collar g moves to a point where the 
spark lever indicates that the ignition is in late position. As 

®ir 0j 


the engine starts, the e rod can be drawn back until the 
collar f engages the spark lever and advances the spark as 
the compression relief cocks are closed. 

In the case of a four-cycle engine having a cam-shaft with 
an endwise movement to bring a double-lipped exhaust cam 
into operation to relieve the compression, the same shaft 
can also bring into operation another cam to control the 
ignition. There are many ways to accomplish this object, 
and, on accoimt of securing greater ease of operation, it is 
suggested that all owners of gasoline marine engines should 
study out some way to make a connection between the com- 
pression relief and spark control 

38. One means of relieving the compression, used only 
in four-cycle engines, consists in having the exhaust valve 
open during a part of each compression stroke; while 
another consists in using cylinder relief cocks screwed into 
openings either through the cylinder walls and covered by 
the piston when near the end of the up-stroke, or into open- 
ings communicating directly \inth the combustion space 
above the top of the piston. Compression cocks are neces- 
Svirily employed in two-cycle engines, and because of their 
cheapness they are finding favor among manufacturers of 
f,x:r-cycle engines. There is, however, an element of 
danger associated with their use, as many boats that have 



been burned would not have tiiken fire except throngh relief 
cocks. When used iu cabin boats, the relief cocks should 
be piped outboard or into the exhaust, for, if there should 
be present in the boat's cabin or under the floor gasoline 
vapor and air in the proportions of an explosive mixture, 
with the relief cock open and shooting a column of flame 
down toward this mixture, an explosion might result that 
would destroy the boat. If compression relief cocks are 
used, they should, therefore, always point upwards instead 
of downwards. Combined relief and priming cocks can 
often be used for priming the cylinders, but separate prim- 
ing cups should always be used where the engine is installed 
in a cabin. 

39. Starting an engine having no reversing gear, but 
v/itb a reversing propeller, is somewhat easier than to start 
with a propeller connected rigidly to the propeller shaft, the 

'^egT^'ered blades of a reversing propeller acting to relieve the 
engine of nearlyits full load, while a solid propeller and shaft 
carry a full load. In the latter case, no governor is required. 
In order to nm the boat astern with an ordinary two-cycle 
engine, the engine is stopped and run in the opposite direction. 
As this is impractical with four-cycle engines, governors are 
quite necessary in all reversing-gear engines of more than (i 
or 8 horsepower, although some makers do not use them at 
all, or not until the engine reaches from 10 to 20 horsepower. 
In case no governor is used, great care should be exercised 
to prevent the engine from running away. As governors 
sometimes fail to act, it is always better, when starting an 
engine, to have the throttle within easy reach, as well as 
the switch, in order to prevent an accident If the engine 
has an auxiliary air supply, as many four-cycle engines do. 
it is usually closed on attempting to start, as it is better to 
have the mixture a little too rich than a little too poor in 
gasoline vapor. 

40. Before starting a four-cycle engine, the operator 
should be satisfied that the inlet and exhaust valves, as also 

q>ark, are correctly timed, that the adjustments are 


correct, that the valves all seat properly, and that they are 
not rusted or stuck in their guides. A drop or two of kero- 
sene oil should be used occasionally on the valve stems. Be 
sure that all the oil cups are filled, that all moving parts are 
properly lubricated, that the sea cock is open, and that there 
is nothing to prevent the free passage of water through the 
cylinder water-jackets and thence outboard. Look out for 
ropes that may be wound up by the propeller ; a few acci- 
dents from this cause will usually teach caution as nothing 
else will. Make sure that the electric-ignition system is in 
good working order by testing it with the current on, if of 
the make-and-break type, or by the buzzing at the spark 
coil if jump-spark ignition is used. Next open the relief 
cocks or push the relief cams into position, turn on the gaso- 
line and see that it runs freely, and turn the engine over 
two or three times as fast as convenient. To facilitate start- 
ing, it is sometimes better to put a little gasoline into each 
cylinder through the priming cocks. This operation is 
called priming. After two or three devolutions, the engine 
should start, when the relief cocks should be closed or the 
relief cams thrown out, and the speed of the engine regu- 
lated by the throttle, the proportions of the mixture being 
regulated by the auxiliary air valv^e or by the needle in the 
gasoline valve, unless a compensating or other form of car- 
bureter is used. If the engine misses explosions, it may be 
that it is throttled too much, but it is more probable that 
the mixture is too rich in gasoline vapor. If the engine 
begins to slow down, give it a little more gasoline, and if 
that does not remedy matters decrease the amount, or 
increase or decrease the amount of auxiliary air. When the 
engine is running satisfactorily, open the oil cups and see 
that they feed properly and that the jump operates, watch- 
ing, of course, for overheated bearings, as in any new piece 
of machinery. 

41. If the engine is directly connected to the propeller, 
there is nothing else to be done except to get the propor- 
tions of air and i^asolinc vapor as nearly right as possible, 


see that lubrication is constant, and that the circulating 
water discharges freely. If the engine has a reversing gear, 
there will be little need of throttling when changing from 
full speed ahead to a neutral position or full speed astern; 
but with a reversing gear and no governor, extreme care 
should be exercised in throwing in either gear or the engine 
may be stopped. The reversing gear absorbs some part of 
the power of the engine, which is more liable to stop when 
attempting to go astern than ahead. It will be necessary, 
in case a governor is not used, to have some practice in 
order to be sure that the engine will not be stopped when 
throwing in the gears, and in order to be able to handle the 
throttle properly. With a governor, however, the manipu- 
lation of the engine is largely a question of properly propor- 
tioning the mixture of air and gasoline vapor and of proper 

43. Once started and running, the engine may not turn 
up to its usual speed, may miss explosions, or may seem to 
labor hard. In such cases, an examination should be made 
to see that the lubrication is sufficient and regular, remem- 
bering that a little too much lubrication is not so bad as 
too little, although an excess of oil in the cylinder may give 
trouble later. As the effect of too much oil is indicated by 
the color of the exhaust, trouble from this source is easily 
discovered and can easily be remedied. 

An attempt should first be made to remedy the trouble, 
if possible, by varying the proportions of the mixture of air 
and gasoline vapor. Then, the electrical connections should 
be examined carefully to see if they are tight. If conditions 
seem to get worse instead of better, it will be necessary to 
stop the engine and search out the trouble, for it would be 
imprudent and possibly dangerous to continue running. 

43. When the engine is to be stopped, first throw in the 
compression relief cam or open the relief cocks. The object 
of relieving the compression is to prevent the engine from 
running after 'the electric current is thrown off, the mixture 
remaining in the cylinders igniting from incandescent 


particles of carbon attached to the piston or walls of the 
cylinder. The switch should then be thrown out and the oil 
cups shut off. When using reversing gears, it is always better 
to stop in the neutral position, neither going ahead nor astern, 
for it is usually much easier to release a clutch when the 
engine is running than after it has been stopped. The 
gasoline-supply valve, which should always be placed in the 
supply pipe directly back of the vaporizer or carbureter, 
should then be closed. 

Among several reasons for adopting this method of pro- 
cedure when stopping an engine the following may be men- 
tioned: If the engine is stopped by entirely closing the 
throttle, its closed position may not be noticed when 
attempting to start, and with the throttle closed the cylinder 
will be filled with a charge of burned gas instead of a fresh 
charge of explosive mixture ; the engfine should not be stopped 
with the switch on and the make-and-break electrodes in 
contact, as the batteries would thus soon be exhausted. 

Shutting off the gasoline at the vaporizer by means of the 
needle valve is extremely bad practice. It is much better 
and more sat isf actor}- to close the valve or cock in the sup- 
ply pipe, for should a leak develop at the union in the 
piping to the carbureter the closing of the needle valve 
would not prevent gasoline from leaking into the lower 
jviirt of the Ixxit. Shutting off the supply at the vaporizer 
in twHvcycle engines is more likely to cause crank-case 
cxpKvidons or Ivick fires than in four-cycle engines. Back 
firing is caused by a too weak mixture of vapor and air, 
which is slow-buniing. In four-cycle engines, more time 
elapses Knwccn the opening of the exhaust and the inlet 
valves than in two-cycle engines, in which the inlet port is 
oiviuxl almv>s: at the same time as the exhaust. The faster 
the twv^-cvc'o or.cir.e nir.s, the less time there is between 
tV.o oix^ v :* :ho twv^ iv^rts and the greater the liability to 

x»«-»»* **C-^ »^X*> '*C' ^"'^ "*- 'X' ^.■" •» •■^ »* ,"~ 

some coerat OTS are 

This is Tir.necessarv 


and is liable to cause more harm than good ; for, were the 
engine to be started with the sea cock closed, considerable 
damage to the engine might be caused by overheating. 
Rubber hose should not be used for the connection from the 
pump to the sea cock, and if suitable piping is here used 
there is little if any danger from a leak developing while 
the engine is not running. 

As a precautionary measure, it is always good practice to 
close the gasoline valve at the tank at the same time it is 
closed at the vaporizer or carbureter. 



46. The proper care of an engine and its auxiliaries 
depends largely on the character of the engine. When an 
engine is exposed to the action of salt water that fre- 
quently comes aboard as spray, it requires more care than 
when installed under cover. While the exterior of an 
engine should always be kept clean, this is not so essential 
as that all bearings and moving parts be kept free from rust, 
gummed oil, and dirt, and that the lubricating system may 
be depended on when the engine is running. Loose bear- 
ings should be remedied promptly, all bolts and nuts should 
be examined frequently, replaced if lost, tightened if loose, 
and where holes are drilled in the ends for spring cotters, 
the latter, if not in place, should be replaced. To avoid 
possible trouble with the gasoline supply and carburization^ 
gasoline tanks and piping should be inspected occasionally 
for accumulations of water and dirt. The carbureter or 
vaporizer should be looked after, and the lubricator sight- 
feed glasses, if clouded so that the feed cannot be seen 
plainly, should be cleaned with kerosene or gasoline. 

Salt water injures machinery, and should by all means be 
kept from the -reversing gear or clutch ; for, in addition to 
its oxidizing effect, the presence of dissimilar metals in the 


salt water gives rise to electrolysis, which is very destructive 
to studs, bolts, gears, shafts, etc. 

In cold weather, the water should be carefully drained 
from the water-jacket, pump, and piping, to prevent it from 
freezing and thus bursting the water-jacket. While burst 
piping can readily be replaced, it is not an easy matter, 
even when possible, to repair a broken water-jacket, or 
even to replace a pump. 

Lubrication of the reverse gearing, clutches, and thrust 
or spring bearings should not be forgotten. The stem bear- 
ing is lubricated by the water, while stuffingboxes are lubri- 
cated by the flax packing, which is usually filled with tallow 
or some similar substance. 

Kerosene will be found very convenient to use in loosen- 
ing gummed oil on bearings and even in the cylinder it may 
be used freely to loosen up accumulations of carbon and 
burned oil. In fact, kerosene is a necessity for occa- 
sional use on valve stems in four-stroke engines or on the 
movable igniter bearings in engines using make-and-break 
ignition. A little vaseline or cylinder oil ma)' be used to 
coat bright parts to prevent them from tarnishing, but the 
former is much cleaner than the latter. Special care should 
be exercised to see that sufficient supplies are always on 
board — aplenty of gasoline, oil, tools, a good reserve battery, 
always a pail to use in case of fire or a bad leak, a dry- 
powder fire-extinguisher to put out possible gasoline fire, 
and a life preserver for each person on board, for personal 
safety is of the greatest importance. 


46. In leaving the engine after a run, the gasoline 
should always be shut off at the tank, and also at the 
valve near the carbureter or vaporizer. The lubricators 
should be closed, and any excess of oil on the engine 
wiped off while the engine is warm. If cold weather i^ 
threatened, drain the water-jacket, pump, and piping, a^d 
cover the engine with canvas, being careful that it does 


not touch an over-heated exhaust pipe, where it is liable to 
take fire. 

When the season is over, and the boat is ready to lay up 
for the winter or the closed season, the engine should be 
taken out of the boat if convenient. If not it should be cleaned 
carefully and the bright parts covered with vaseline, white 
lead and tallow, or something that will protect the parts and 
still be easily removable. Plenty of cylinder oil should be 
left in the cylinder, the flywheel should be turned over two 
or three times, the piston being left on the outer center to 
prevent any possible rusting of the upper surface of the 
cylinder, where it is quite important that there should be 
a smooth surface. A multiple-cylinder engine should be 
turned over occasionally to guard against similar trouble. 
If the engine is to be left in the boat, it should be protected 
with a water-tight covering, no part of which should be 
allowed to touch the engine, as such contact is very sure to 
cause rusting. 

If these precautions are carefully observed, very little 
trouble should be experienced in putting the engfine in com- 
mission at the beginning of the season. It may be well to 
remove a large part of the oil put in when the boat was laid up; 
the engine should then be as easy to start as when put away. 


47. A few tools are always necessary in running a 
marine gas engine to get at or remove parts that may have to 
be taken down for adjustment, repair, or inspection. A 
pipe wrench is indispensable, also a good-sized adjustable 
monkey wrench (say about a 14-inch), a small and a large 
screwdriver, pair of adjustable hawk-bill plyers, bicycle 
wrench, three-cornered and half-round second-cut or bastard 
files, 8 and 10 inches long, respectively, light round peen 
hammer, {^-inch cape chisel, two or three cold chisels of 
diflEerent lengths, a center punch, a small round nail set, and 
such other small tools as may be useful in case of emergency. 
The tools liable to rust can be carried conveniently in a 


waterproofed canvas roll, where they may be found when 
they are required; but the pliers, on account of their fre- 
quent use, might better be carried in the pocket. One of 
the most convenient tools on board a boat is a small hand 
vise, similar to those used by electric linemen. It will hold 
almost an3rthing it may be desired to file, and Tvhile not 
absolutely necessary will often be found a convenience. 

Tools are of little use unless there is at hand an assort- 
ment of supplies, including shellac, strong cotton cloth, 
insulated wire, soft copper wire, hard bronze spring wire of 
different sizes, insulating tape, some strong cord, small 
pieces of canvas, some soft sheet brass or copper .003 or 
.005 inch thick, and, if possible, a roll of gasket material in 
a water-tight tin box to prevent it from becoming wet or 
broken. An assortment of nuts, cotter pins, etc., as well as 
duplicate small parts liable to become broken, such as igniter 
springs, could be carried in a spice box to obviate a serious 






!• In selecting a stationary gas engine there are sev- 
eral important points to be considered, and the engine that 
embodies the greatest number of desirable qualities is the 
one to be preferred. First of all, the engine must possess 
sufficient capacity to accomplish the desired work. It 
must also be adapted to the requirements of speed, regula- 
tion, and direction of running imposed by the work to be 
done. It should be economical in fuel consumption, relia- 
ble in service, and of simple construction. 

2, In determining the size of an engine for a given 
amount of work, it should be borne in mind that an engine 
that is called upon to run at its full capacity during the 
greater part of the time is actually overtaxed. Working an 
engine to this extent will result in rapid wearing of the 
cylinder and piston, and consequent loss of power and 
economy due to leakage. When doing the maximum 
amount of work possible in a plant, the engine, if 
governed by the regulation of the number of impulses, 
should cut oflE at least once in four or five charging strokes. 
This will benefit the cylinder through the admission of 
charges of pure cool air at more or less regular intervals. 

CopffigkUdhy Iniemaiknai Textbook Company, Entered at Stationers* Halt, London. 



3. The type of engine decided on should be the one 
most suitable for the work it is to do. Engines for opera- 
ting electric generators, especially for lighting purposes^ 
must run with greater steadiness than is generally required 
for ordinary power. There are other cases — such as the 
operation of sensitive typesetting machines — where a very 
steady speed is desirable. The question whether a horizon- 
tal or a vertical engine should be selected must be settled 
with a view to local conditions of available space and the 
character of the work ^o be done. 

4. The consumption of fuel should always be in propor- 
tion to the work performed by the engine. The g'ovemor 
should respond promptly to any fluctuation in the load, and 
the friction loss should be kept at a minimum by proper 
methods of lubrication. The attainment of good results 
depends largely on careful workmanship, as well as on prop- 
erly proportioned valves and liberal bearing surfaces. 

6. The engine should be capable of being started 
promptly without great exertion, of developing its rated 
horsepower, and maintaining a steady speed, while con- 
suming the normal amount of fuel. 

6. Other things being equal, the engine that is simplest 
in construction and operation is to be preferred. This, 
however, should not be carried to a point where reliability 
of running and accessibility of the working parts are sacri- 
ficed. All the working parts, such as piston, connecting- 
rod, valve gear, igniter, etc., should be in plain view and 
easy of access for cleaning and necessary repairs. 


7. Even a casual inspection will reveal to the eye of a 
mechanic certain evidences of good or bad workmanship. 
Among the points that should be observed are the condi- 
tion of the threads and the fitting of the nuts and their 
wrenches. Threads should be full and smooth, and the 


nuts should fit so as to enable them to be turned by hand on 
the studs or bolts, although they should fit snugly — that is, 
-without play. The jaws of the wrenches should fit the 
nuts exactly. The fit of pins, levers, or links can be 
inspected by moving them by hand, when they should 
slide smoothly and evenly. Whenever possible, moWng 
parts subject to wear should be properly hardened to a 
moderate depth below the outer surface. This refers espe- 
cially to cams, rollers, blades, and pivot pins. 

8. When in motion, the good workmanship of an engine 
is indicated by smooth and noiseless running. There should 
be no pounding or clattering sound, which would indicate 
lost motion and loose-fitting bearings or piston.- The fly- 
wheels should run true and without vibration. If the rim 
of the wheel should show any vibrating motion at the time 
of the explosion, it would be evidence of weakness either 
in the crank-shaft or in the wheel itself. The proper balance 
of the revolving and reciprocating parts is indicated by the 
absence of any forward and backward sliding of the engine 
bed on its base or foundation. 

9. When the engine is operated with illuminating gas, 
the consumption of fuel is best determined by reading the 
meter at the beginning and at the end of a certain period of 
time while the engine is running under its rated load. As a 
rule, manufacturers guarantee the power and the gas con- 
sumption per brake horsepower under full and partial loads. 
A gasoline engine should be tested as to its fuel consumption 
by connecting the pump to a graduated bottle of about 
1 gallon capacity, and the amount used for a certain period 
should be noted. A good engine, running with ordinary 
stove gasoline, should use about a pint of fuel per brake 
horsepower per hour when running under its rated load. 

10. Before deciding on the make and type of engine 
contemplated for a certain purpose, it will always pay to 
investigate the working of engines of the same manufac- 
ture that have been in use for a reasonable length of 


time. Reports from reliable users will go far towards deter- 
mining the actual merits of an engine, its economy, the 
amount of repairs it may be expected to require, and other 
matters of vital interest to the power user. 



!!• The selection of the most suitable location for an 
engine deserves careful consideration. The space to be 
occupied by the engine should, if at all possible, be sepa- 
rated from the rest of the room by a partition. Sufficient 
space should be allowed around the engine, especially on 
the valve and governor side, where the space should be not 
less than 3 feet, to permit of easy access to any part of the 
engine. In all factories or shops where the presence of fly- 
ing d\ist IS unavoidable, it is necessary that the engine room 
should be surrounded with dust-proof walls. A room 
well lighted and ventilated is a great help in keeping the 
engine in proper condition, since it allows the attendant to 
watch closely the lubrication, valve motion, action of the 
go\'cmor, etc. The \ise of an open belt is always preferable 
to a crossed belt running from the engine to the line shaft 
The engine should be set in relation to the direction in 
which the shafting or machines to be driven will revoh^, 
and the question of open or crossed belt should be decided 
with this point in \new. The distance between the centers 
of the engine shaft and the line shaft or the machine to be 
openiteil should never be less than 10 feet for engines up to 
10 horsepower, and from 1*2 to *20 feet for engines of larger 


fi. Fonndatlon Templet. — The location of the engine 
hav!!*^ K^ev. v'otcrr.'.inov:. the fv^v.ndation may be prepared. 
r'.»i!::> .iv.vl sixvinc^itior.s ^l\-i::ir the size, depth, and material 


of the foundation are usually supplied by the builders of the 
engine, and in many cases a templet is also provided by them. 
This templet is a rigid framework, made of 1-or l^inch 
boards from i to 6 inches wide, in which holes are bored cor- 
responding to the holes in the engine bed through which the 
Itoldlng-do'svn, or fbtuitlatlon, bolts-must pass. If the 
templet is not pronded by the maker of the engine, it should 
be constructed in accordance with the dimensions given on 
the foundation drawing. If the engine bed is at hand, it is 
well to measure the distances between bolt holes, and com- 
pare these distances with those shown on the drawing. If 
they do not agree, as is sometimes the case, the holes in the 
templet should be located by measurements taken from the 
engine bed. The engine builders often furnish the founda- 
tion bolts, nuts, washers, and anchor plates. 

The center lines of the cylinder and crank-shaft should be 
marked on the templet with a scriber. In setting the tem- 
plet, care ehotild be exercised to have it the required height 
from the floor, level on top, and square with the building. 
This is done because the templet is tosed to determine the 
height of the top of the foundation bolts as well as their posi- 
tion laterally. If the shafting to be driven is in place, the 
center line of the crank-shaft as marked on the templet must 
be brought parallel with that of the line shaft To accomplish 
this, drop two strings with weights attached, one on each 
side of the foundation and several feet away from it, from 
the line shaft to the floor. Then set the templet so that a 
string drawn across it, and exactly in line with the center line 
of the crank-shaft, is the same distance away from the two 
plumb-lines suspended from the line shaft. The crank-shaft 
will then be parallel with the line shaft, so that they may be 
connected by pulleys and belt. 

13. Placing Ponndatlon Bolts. — After the templet has 
been set and securely propped up and fixed in position, the 
foundation bolts should be inserted, allowing the top ends to 
extend the proper distance above the boHom of the templet. 
nMnp.ttbft aiU»^«i)d wa^iera are in place, ao that tiie enda of 


bolts project slightly beyond the nuts, the distance above 
the bottom of the templet should be adjusted so that it will 
equal the distance that the bolts should project above the 
top of the foundation. 

In order to guard against any slight shifting of the foun- 
dation bolts while the masonry is being put in place, or 
against discrepancies between the foundation plan and the 
engine bed, it is advisable to surround the bolts with wooden 
casings or, preferably, with iron pipes about 1 inch larger 
on the inside than the diameter of the bolts. This will per- 
mit the bolts to be moved slightly in the fotmdation and 
their location to be adjusted to suit the actual measurements 
of the engine bed. 

14. Boildlngr tlie Fotmdation. — ^The building of the 
foundation may now be undertaken. If brick is used, 
it should be of the hard-burnt quality, and should be laid 
in mortar made from a good quality of Portland cement and 
clean, sharp building sand, with a sufficient amount of water 
to render the mortar of the proper consistency. Common 
brick or building stone may be used for the inside of the 
foundation, but the outside should be faced with pressed 

In many cases, a foundation of concrete is cheaper or more 
convenient to construct than one of brick or stone, and, if built 
of a proper grade of material, is preferable to a brick founda- 
tion. A good mixture of concrete may be made of five parts, 
by volume, of broken stone, about 1^ inches in size, two parts 
of clean, sharp sand, and one part of Portland cement, adding 
water in proper quantity and thoroughly mixing the material 
to jri\'e it the required consistency. After the pit has been 
filled with concrete up to the floor level, build or place a box 
under the templet, the inside measurements of which should 
correspond with the size of the part of the foundation that 
projects above the floor. Pill the box with concrete, and do 
not remove it until the mixture has become well dried, which 
^ijcnerally requires from 3 to 4 da\*s. After the box has been 
ro moved, the sides and top of the foundation should be 


finished with cement mortar, so as to give it a smootb 
appearance. The templet should not be removed until the 
foundation has completely dried, as there is danger of the 
bolts being drawn out of their proper position during 
the setting of the foundation, 

A properly built concrete foundation becomes as hard as a 
solid mass of stone. Brick foundations for large engines 
should, if possible, be topped with a cap of sandstone or similar 
material. Oil has a deteriorating effect on concrete or brick 
foundations. In order to protect them against the injurious 
action of any lubricating oil that may accumulate on top, it 
is well to provide a sheet-metal oil pan in which to place the 
engine bed, or to have a 3-inch plank covered with sheet 
metal to form the top of the foundation for engines of small 
or medium size. 

The depth of the foundation required depends on the 
nature of the soil, and the pit in which the foundation is to 
be built should be dug down to solid earth. The distance it 
is necessary to dig in order to reach solid earth determines 
the length of the foundation bolts. They should extend to 

I within 6 to 13 inches of the bottom of the pit. The anchor 
plates, which are attached to the lower ends of the bolts, 
should be of ample size, so as to prevent any yielding of the 
fotudation material when the bolts are tightened. 

15. Preventing Vibration, — To prevent the vibrations 
caused by the explosions in the engine cylinder from being 
communicated to the building, the engine foundation should 
be kept free from contact with the foundation walls of 
the building. This is of special importance in office buildings, 
stores, etc In cases where such vibrations are very objec- 
tionable, it is advisable to take the precaution of placing the 
foundation on a cushion formed by a 6-inch layer of mineral 
wool, tan bark, or some other insulating materiaL This 
should be placed not only beneath, but also all around the 
sides of the underground portion of the foundation. Cush- 
ioniag the foundation in this manner not only prevents the 
_ iKUtHais&ioa of .vibratUin, but also prevents the noise cauied 


by the running of the engine from being communicated to 
the rest of the building. A large and heavy foundation also 
tends to prevent the transmission of vibration, and when the 
engine is securely bolted to such a foundation most of the 
vibration of the engine will be absorbed by the foundation. 

16. Tlmibep Foundations. — In localities where brick, 
concrete, or stone foundations are not to be had, timbers may 
be used. They should be of such length as to project sev- 
eral feet on each side of the engine bed. If several timbers 
are required to make up the desired height or width of the 
foundation, they should be bolted together in a substantial 
manner. The bolts that hold the engine to the timbers 
should extend through the entire depth of the timbers and 
be provided with large square heads fitted in countersinks of 
corresponding size to keep the bolts from ttuning when the 
nuts are tightened. 

1 7. Support of Engrlnes on Floors. — Engines of small 
or medium size are frequently set on upper floors, where a 
brick or concrete foundation is out of the question. In such 
cases, the engine is usually provided with a heavy cast-iron 
base of sufficient height to allow the flywheels to clear the 
floor; the heavy base absorbs a considerable portion of the 
vibration, and in a measure takes the place of a foundation. 
When located on an upper floor, the engine should be set in a 
corner near the walls, to avoid springing the joists. In every 
such case, the floor boards should be removed and a thor- 
ough inspection of the condition of the joists made, so as to 
be sure that they are of ample strength to sustain the weight of 
the engine and absorb the shocks caused by the explosions. 
Preferably, the engine should be placed so that the length 
of the bed extends across the joists. In order to take in as 
many joists as possible, 3-inch planks or heavier timbers 
projecting several feet on each side of the bed should be 
placed under it, and held to the joists by bolts extending 
through and secured by anchor plates underneath. The 
engine should be fastened to the plank by bolts in the same 
manner as in the case of the timber foundations. 


1 8. Placing Sng^ine Bed on Foundation. — After the 
engine bed has been brought alongside the foundation, 
blocks are placed on top of the masonry high enough to clear 
the tops of the foundation bolts. The bed is then moved and 
set upon the blocks and gradually let down by inserting planks 
and removing the thicker blocks. Generally the bottom of 
the bed is planed smooth, so that, if the top of the founda- 
tion is level and smooth, the bed will rest firmly on the 
foundation. Any unevenness in the surfaces of the founda- 
tion or of the base of the bed must be taken up by wooden 
or iron wedges, which are inserted and adjusted until a spirit 
level applied to the engine indicates that it stands perfectly 
level. After the engine is leveled up, the nuts of the foun- 
dation bolts should be tightened gradually and evenly with- 
out straining the engine bed. If tightened carelessly, the 
bearings of the engine in the bed may easily be drawn out 
of line and cause serious trouble with hot boxes as soon as 
the engine is started. 

19. Grouting:. — After the bolts are tightened mod- 
erately, the space between the bedplate and the foundation is 
filled with grouting. The grouting may be made of iron 
borings mixed with cement, sal ammoniac, sulphur, and 
water in about the following proportions: two parts of sal 
ammoniac, one part of sulphur, five parts of cement, and 
forty parts of iron borings mixed with enough water to. make 
a heavy paste. This mixture rusts firmly into place. A 
joint made of a rusting mixture is generally called a rust 
Joint. Sometimes, melted sulphur alone is used, but one of 
the best gfroutings and the most easily* applied is pure Port- 
land cement mixed with water. The rust joint must be 
well tamped into place, while the sulphur and cement will 
flow in, suitable dams being constructed to hold it in its 
proper place. Bolt holes should also be filled with liquid 
grouting. Some builders, who use hollow bedplates of box 
form, fill the entire bedplate with concrete, to give it solidity 
and to reduce the tendency to excessive vibration from 
the knocking caused by loose bearings. 

1»K— 20 

... - 4.:, .• 



S0< Arrangement and Sizes of Piping, — It is custom- 
ary for the engine manufacturer to supply a general piping 
plan, giving a diagram of the various pipes and their sizes, 
for the fuel-supply, the water-inlet and overflow, and the 

exhaust pipes. The general scheme of these connections for 
the gas and exhaust piping, subject to changes according to 
local circumstances, is shown in Fig. 1. The gas enters 
through the pipe a, and flows through the valve ^ to the gas 




bag c. From c^ it passes through the pipe d to the engine 
cylinder e. The exhaust gases pass from the cylinder through 
the pipe /to the muffler^, and thence out of the pipe h to 
the atmosphere. The gas bag is furnished with the engine, 
and serves as a reservoir, which is necessary because the 
charges are taken into the engine suddenly and at intervals. 
During the suction stroke the gas bag will slightly collapse, 
and if the pressure should accidentally fall below the normal, 
the collapsing of the bag may partly close the gas pipe enter- 
ing it. To guard against this, the pipes should extend well 
into the bag, that is, from 6 to 12 inches, according to the size. 
To prevent absolutely such interference with the supply, the 
pipe may run through the entire length of the bag, the gas 
entering through a series of holes drilled into the pipe. 
About twenty holes, varying in size from J to 1 inch in 
diameter, according to the size of the engine and supply 
pipe, will be sufficient 

To obtain the full power that the engine is capable of 
developing when using illuminating gas, the size of the gas- 
supply pipe must be ample to permit the gas to flow without 
reduction of pressure, and will depend on the distance 
between the engine and the street main. Table I gives a safe 
estimate for the sizes of pipe to be used at different distances 
from the engine for light pressures of from 1^ to 2 ounces. 



Horsepower of 

Diameter of Pipe, in 


Within 15 Feet 
of Engine 

Further Dis- 
tance of 90 Feet 

Further Connec- 
tion to Main 





3 to 5 




6 to lo 




II to i8 




19 to 28 




29 to 45 




46 to 65 




66 to 100 







31. Pressure Begrulator. — In cases where the fluctua- 
tions in the gas pressure must be considered, and where the 
surrounding gas lights would flicker owing to the intermit- 
tent drawing of gas from the main during the working 
of the engine, a pressure regulator should be installed. 
One form of regulator is shown in Fig. 2. It consists of a 

balanced valve a, the stem of which is connected to a dia- 
phragm ^, and a helical springs, the tension of the latter 
being adjustable. The gas enters at d and leaves at f, the 
diaphragm d being therefore subjected to the pressure on the 
outlet side of the valve. If this pressure increases, the dia- 
phragm is forced downwards, and the valve is closed to a 
greater or less extent, tlius throttling the gas supply and 
lowering the pressure on the outlet side. By adjusting tlte 
spring c, any dfsired pressure may be constantly maintained 
at e regardless of variations in the pressure on the inlet side. 

The regulator must be placed in the supply pipe, so that 
tlic gas will pjiBS th roiigh the valve before it reaches the rub- 
ber gas bag c. Fig. 1. 

A valve sliown at ^ should be placed in the supply pipe, so 
as to shut oti the gas before it reaches the bag c, and should 




be within easy reach, to be opened or closed when starting 
or stopping the engine. As oil has a damaging effect on 
rubber, the bag should be inclosed in a suitable box or 
cover, in order to protect it from lubricating oil that might 
be thrown upon it by the revolving parts of the engine. 

33. Gas Meter. — To permit a strict account of the gas 
consumption of the engine to be kept, a meter registering 
the amount of gas used by the engine should be installed. 
The meter should be placed as near as possible to the engine. 
The following capacities of meters may be considered ample 
for engines of various sizes working under normal condi- 
tions, the meters being rated according to the number of 
lights they will supply. 




Size of Meter, in 

Rated Number 

of Lights 


Size of Meter, in 

Rated Number 

of Lights 



26 to 35 


3 to 5 


36 to 45 


6 to lo 


46 to 55 


II to i8 


! 56 to 70 


19 to 25 


71 to 85 


/53« Piping for Natural Gas. — The pipe connections 
for natural gas are essentially the same as for illuminating- 
gas. As a rule, natural gas is supplied at a higher pressure, 
which must be reduced by a suitable regulator to about 2 to 
4 otmces before it reaches the reservoir near the engine. 
Owing to its greater heating value, a smaller amount of natu- 
ral than of illuminating gas is required for developing the 
same power, the proportion being about 75 or 80 per cent. 
The size of the supply pipe near the engine may therefore be 
proportionately smaller for natural gas than the sizes given 
in Table I for illuminating gas. 

24. Bxhanst Plplni?. — The object of the exhaust pipe 
is to carry the waste gases or products of combustion into 




the open air. To do this effectively and with the least resist- 
ance or back pressure, the pipe should be of ample size and 
should run as straight as possible, avoiding any sharp bends. 
As the gases leave the cylinder at considerable pressure, the 
exhaust is noisy unless provision is made for muffing the 
sound. This is usually accomplished by inserting a cast-iron 
muffler, as shown at gy Fig. 1, in the exhaust . pipe near 
the engine. A flange union should be provided between the 
exhaust pipe and the engine, and between the exhaust pipe 
and the muffler, to facilitate the disconnecting of the pipe in 
case the exhaust valve or the cylinder head needs repairing. 
In placing the muffler and connecting it to the exhaust outlet 
of the engine, care should be taken to give the pipe a certain 
amount of flexibility, as a rigid arrangement would strain the 
exhaust-valve casing, owing to the expansion of the pipe 
when it becomes hot. This would result in rendering any 
packing between the cylinder and exhaust-valve casing 

leaky, an annoyance 
that can easily be 
avoided by a judicious 
arrangement of the 
muffler and pipe con- 
nections. The most 
efficient way to avoid 
this difficulty is to use 
an expansion joint. 

one form of which is 
shown in Fig. 3. The 
end a of the pipe leading from the engine is free to move longi- 
t udinally in the fitting A, which is screwed tightly on the pipe c 
loading to the muffler. The nut </, when screwed down, com- 
presses the |\icking rand prevents leakage between the pipe^ 
and the tittin>r b. The expansion joint is thus a simple form 
i^t stuffln^K^x. the piicking beinir of asbestos wick thoroughly 
hibnoatovl with c^^at^hite. Extension and contraction due to 
v^aT\>:x\< v^f oaiise the p:pe a to move in and out 
v>t the t^ttir.c > \vi:hov.t strainir.g the pipe connections. The 
pijH" tn>m the n:;:f*'»or to the open air should never be smaller 



than the outlet on the engine. If a long pipe with several 
bends is unavoidable, the size of the pipe should be corre- 
spondingly enlarged. 

25. To avoid causing annoyance, from the exhaust gas, 
to people in neighboring buildings, the exhaust pipe should 
be carried above the roof of the building. If this is done by 
way of a convenient flue or chimney, the pipe should 
be carried up through the entire length of the flue. If 
the pipe terminates inside of the flue, there is danger of 
unbumed gases accumulating in the flue and doing serious 
damage when fired by the first hot exhaust issuing from the 
pipe. As the exhaust gases cool during their passage 
through the pipe, a certain amount of water collects in the 
pipe due to the condensation of the water vapor in the 
exhaust gases. To permit the exhaust connections to be 
drained, all vertical exhaust pipes should be fitted with a T 
at the bottom, one opening of the T being provided with a 
plug or drain cock. 

In densely populated or crowded residence districts, where 
even the muffled sound of the exhaust might become objec- 
tionable, the noise can be entirely eliminated by injecting a 
very small stream of water into the exhaust pipe. A portion 
of the overflow from the water-jacket may be used for this 
purpose. The connection should be made about 4 to 6 inches 
below the exhaust outlet on the engine, to guard against 
any water coming in contact with the exhaust valve and 
poppet. A J-inch pipe will supply enough water to deaden 
effectually the noise from the exhaust of a 20-horsepower 
engine. The water has the effect of cooling and decreasing 
the volume of the hot exhaust gases, and the greater portion 
of the water is carried away with the gases in the form of 
steam. A drain connection must be provided at the lowest 
point of the exhaust pipe, and this must be kept open con- 
stantly, to permit any surplus water to run off to the drain 
pipe or sewer. 

In running the exhaust pipe through wooden floors or 
partitions, metal plates should be used around the pipe, 




allowing 3 or 4 inches clearance between the pipe and the 
floor to protect the woodwork from danger of fire. For the 
same reason, the exhaust pipe, if placed on a wooden floor, 
should rest on bricks or similar material. If the exhaust 
outlet ends in a vertical pipe, it is advisable to place an 
elbow at the top end, to prevent water or solid obstacles 
from getting into the pipe. 

36, Piping for Gasoline. — Considerations of safety, 
embodied in the regulations laid down by the National 
Board of Fire Underwriters, require that the supply tank of 
a gasoline engine be placed about 30 feet from the building, 
and below the level of the engine-room floor, making it 
impossible for the gasoline to flow to the engine by gravity. 
Such an arrangement is shown in Fig. 4, with the engine 
at rt, the gasoline tank at ^, and the pump at c. The tank b 
should be so placed that the bottom of the tank will not be 
more tlian 5 feet below the level of the pump i\ as, owing to 
the nature of gasoline, it cannot well be raised through a 
greater height even with a well-constructed pump. The sup- 
ply pipe d is attached at the bottom of the tank, and should 
have a constant rise toward the engine. The tank is placed 
preferably in a brick-lined vault, large enough to allow access 
to the valve e or other valves in pipes near the tank. The 
overflow pipe/", through which the gasoline returns from the 
cup ^ to the tank, enters the tank above the supply pipe d, 
A drain cock must be placed at the lowest point of the tank, 
to allow any water that may accumulate there to be drained 
off. Moreover, the gasoline may contain a little water, which, 
being heavier, will settle to the bottom of the tank, and 
in time will increase in quantity to such an extent as to be 
drawn into the engine and cause it to stop. 

27. Stop-cocks should be provided in both supply and 
overflow pipes near the tank. They may be closed, so as 
to allow the pipes and connections to be examined without 
having to empty the reservoir. A stop-cock in the supply 
pipe, to be closed when the engine ib shut down overnight, 
has the additional advantage of keeping the pijxj filled 


with fuel and obviating the necessity of having to pump it 
up by hand before starting the engine in the morning. It is 
very important to have all joints in the gasoline pipes per- 
fectly tight. Galvanized pipe and fittings should be used and 
all screwed joints soldered. Before the pipes are put in 
place, they should be thoroughly cleansed of any impurities 
by washing with kerosene. All pipes and fittings should be 
carefully examined to make sure that they show no defects, 
such as imperfect seams or blowholes, that would admit 
air into the pipe and prevent the pump from lifting the 

A filter, shown at A, Fig. 4, is usually furnished with 
the engine; it should be placed in the supply pipe before 
the point where this pipe enters the pump. Neglect in 
supplying a filter may result in impurities being washed out 
of the pipe, settling under the pump valves, and interfering 

Pio. 5 

with the action of the pump. In case no filter is supplied 
by the maker of the engine, it is well to provide one. In 
Fig. 5 is shown a good form of filter, which is made of fine- 
wire gauze a inserted in a short nipple b and held in place by a 
standard brass union r, the gasoline passing through in the 
direction of the arrow. The gauze is held in place by a brass 
ring dy and the joint is made tight by a leather washer e. 
In running the gasoline pipe to the engine, care should be 
taken to keep it away from the exhaust pipe, as the heat 
from this pipe would interfere with the flow of gasoline by 
producing a quantity of gas in the pipe that would prevent 
the liquid from being pumped up into the engine. Gasoline 
pipes that are placed underground should not be covered with 
earth until a test has proved that they are perfectly tight 


It is well to make sure of this by starting up the engine, 
keeping it running for a day or two with the pipes exposed, 
and watching for leaks. To facilitate taking down any pipe 
connections near the engine or disconnecting the tank, use 
brass unions in the gasoline pipes near the pump and the tank. 


28. Temperature of Cooling: Water. — In a well-con- 
structed gas engine having ample cooling water space around 
the cylinder and valve-casing, the water supply should be so 
regulated as to maintain a temperature of about 160° to 
180® F. This temperature will prevent excessive heating, which 
wotdd interfere with the proper lubrication of the piston and 
cylinder and with the easy operation of the valves and igniter, 
as well as destroy the packings between the cylinder and the 
valve casings, where such packings are employed. 

Keeping the temperature of the cooling water much below 
160° F. would have an injurious effect on the condition of 
the piston and cylinder, and prevent getting the best results 
from the engine, even with a proper combustion of the mix- 
ture in the cylinder. If the water when it leaves the cylinder 
is practically cold, the cylinder will be cooled to such an 
extent as to cause condensation of the exhaust gases, result- 
ing in corrosion, imdue wear of the piston, and sticking of 
the piston rings, and a large amount of heat that should be 
utilized in doing work will be carried away by the water. 

29. Tank System of Cooling. — For engines of small or 
medimn size, cooling by means of a water tank, as shown in 
Fig. 6, is most efficient and least expensive. When employ- 
ing a tank of proper size, the question of keeping the water 
at the proper temperature is easily solved. The amount of 
water that must be added in this system of cooling is limited 
to the small quantity that is lost by evaporation. The essen- 
tial points to be observed in making connections between 
the engine and the tank are as follows: The tank must 
be of such shape that the opening for the pipe a at the top 


is at least 3 feet above the top of the engfine cylinder i. Th 
pipe must be of ample size, so as to afford little obstmctioi 
to the circulation of the water. The water should be talei 
from a convenient point immediately above the bottom o 
the tank, and should enter the cylinder jacket at the bottoi 
and leave at the top. The level of the water in the tanl 

•liiMiki always \ c several iiK'hcs abuve the entrance of t 
lv^iiot- pijv It ncir \\k- top of the tank. A drain cuck c shou 
'.■ j'I.iolhI at thi' 1. ivi-sl point <'t the pipe, to allow the water 
V ilr.uvn ntT !i ci'!i! weather, and thus prevent freezii 
n.l 11 >T' SOI I ;',—.: ^i;-sting; of t^c water-jacket The vertii 
'■jv ;' i:;-v.\ iVo i.;ekot lo c'-.o shoitUI Ix; extended frc 


6 to 12 inches above the water level in the tank, as shown, to 
allow for the escape of air and to facilitate the circulation. 
Where the engine is not placed on a rigid foundation, short 
pieces of rubber hose ^, f should be inserted in the hori- 
zontal pipes at top and bottom, so as to prevent the com- 
munication of any vibration from the engine to the tank. 
The valves g and h permit the tank to be shut off when the 
cylinder jacket must be drained. 

30. The capacity of the cooling- water tank for an engine 
running under an approximately full load may safely be put 
at 50 gallons per horsepower. For large engines, above 20 
horsepower, the tank system of cooling may be successfully 
employed, if supplemented by a circulating-water pump 
driven from the engine or any part of the line shaft. The 
pump must be so set and connected as to take water from the 
bottom of the tank or cistern, force it through the jacket, 
and return it to the tank. If the cistern or tank capacity is 
limited, which is likely to be the case in large installations, 
the use of suitably constructed air-cooling arrangements is 
necessary. These arrangements generally consist of a series 
ot slanting surfaces, one below the other; the water, after 
passing through the engine, is delivered by the pump to the 
top of the cooler, and descends by gravity, flowing over the 
surfaces and being cooled by contact with the air, before it 
returns to the tank or cistern. The capacity of the water- 
circulating pump should be about 15 gallons per horsepower 
per hour. 

31. Coollngr by Steady Water Supply. — Where a 
steady supply of cold water from water mains or any other 
source is convenient and inexpensive, the supply pipe can be 
of smaller size than when using the tank or circulating sys- 
tem of cooling. A J-inch pipe at moderate pressure will 
supply enough water for a 5-horsepower engine and a 1-inch 
pipe is sufficient for a 40-horsepower engine, larger engines 
requiring proportionately larger supply pipes. The water 
supply pipe, shown at rt:,* Fig. 7, should enter the engine at 
the ix>int that is likely to heat most rapidly, generally at the 



exhaust-valve casing or cylinder head, and the outlet pipei 
should emerge from the top of the cylinder jacket. The 
outlet pipe should discharge into a funnel c, in order that it 
may readily be seen whether the water is flowing or not, 
and that the temperature of the water may be better observed. 
The overilow pipe </ should be one or two sizes larger than 

the supply pipe, in order that all the water that is 
brought to the engine under pressure may flow off by 
gni\ity. Pro\nsion should always be made by a suitably 
placed dniiii conueclion t* for emptying the cylinder jacket 
in C(.4d n'oathor, to guard against craddngof the jacket vails 
thrvmgh the fn.>eEing of the water. 

S^. IK'ptisits lu Water-J^acket. — If the cooUng water 
Cv>ntnin!i lime or alkali, the heating of the water in the jacket 
will i.\»uj<" thcso solid substances to be deposited in the cooling 
sjviocs. This will six^n choke any narrow ports and preveiit 
pT\''jXT ciivul.itiv^n. Tvsulting in overheating, rapid wearing of 
tV.o valvvs. .mii Kiss of power and eflBciency. A simple 
:x-:'.-vv'.y vv.^xsts ot t'-.e appMcaiion. at regular intervals, of a 
\*','v.;e Av-,;:-".-r. o; hy^ir^x'hlorv, or manatee, acid, made as 
;V".,-ns- '."*'■.■.:!." OT^e 'Air; o:" — ^r'^rc scidwiA rineteeu parts 
,-; w.;:,r, .1".,', A'tcv v:--.-~"-:ir :'-e -jcket cvinpleteh-, po=r:= 
<.— ,-.\c^ of :V #,•"":■.!•. :o r" :V.e enriv cvwEi;? space. AToir 
*.V ■.•".\;"Tv '.o-vr'-vr-. ir, ;'^f ■.u-ke: ^.r- sot-^core z'rsr. ^ t' U 


hours, after which wash the cooling space thoroughly by 
loinning clear water through it. If the solution is permitted 
to remain in the jacket longer than the period stated, there 
is danger that the metal may be damaged by the action of 
the acid. The acid will soften and dissolve the lime or 
alkali, and the clean water will remove it from the jacket. 
It is generally sufficient to apply this method of removing 
the deposits once every two weeks. If neglected too long, the 
acid will not dissolve the deposit. 


33* Shaft and Flywheels. — Before assembling any parts 
of the engine, they must be thoroughly cleaned of any dirt, 
dust, antirust, or packing material, and lubricated where 
necessary. After the engine bed has been securely placed 
upon the engine fotmdation, the working of the crank-shaft 
in its bearings should be examined to see that it turns 
easily. Only very small engines are usually shipped with 
the shaft in place and the flywheels keyed to the shaft. If 
the wheels are shipped separately, they should not be put on 
the shaft until it has been ascertained that the latter does 
not bind in the journal-boxes. When lifted by hand, 
the crank should drop by its own weight from a horizontal 
position. The timing of the valves and igniter depends on 
the relative position of the teeth in the gears on the crank- 
shaft and cam-shaft. As a rule, the gears are marked by 
ciphers or similar symbols, and must mesh so that the mark 
on the tooth of one gear comes opposite to a like mark on 
the space between two teeth of the other gear. This should 
be investigated before any attempt is made to put the wheels 
on the shaft 

34. See that the bore of the flywheels and the surface 
of the crank-shaft are clean. Then oil both parts with lubri- 
cating oil. Usually each wheel and each key is numbered, 
and care should be taken to place them so as to go on the 
side marked with corresponding numbers on the end of the 


shaft. If the weight of the wheels makes lifting by hand 
impossible, place planks on the floor underneath the crank- 
shaft, and roll the wheels up on these plants until the bore of 
the hub stands exactly opposite the end of the shaft 'I'hen 
work the wheel gradually over toward the shaft until it rests 
against the end of the shaft. By a concerted eflEort of the 
men handling the wheel, it will then be easy to slide the 
wheel on the shaft for a distance of an inch or more. Now 
place a block of wood betwefen the crank and the engine bed, 
so as to prevent the crank from moving when turning the fly- 
wheel to the right. Be careful, however, to place the wood so 
as to avoid danger of breaking the bed. Then, while one or 
two men hold and balance the wheel, turn it slowly and 
gradually around on the shaft toward the right, at the same 
time pressing it on the shaft until it is worked on the shaft 
the full length of the hub. Remember that the wheel has 
been on the shaft before, and if it is found that it sticks and 
refuses to turn, look for obstacles such» as dust or chips, 
and take off the wheel at once before the bore of the wheel 
and the surface of the shaft are damaged by cutting. 

35, After the wheel has been put on the whole distance, 
turn it so that the keyway in the wheel stands exactly oppo- 
site the one in the shaft, and drive the key in by means of a 
sledge or a large-sized hammer. The keys should be well 
lubricatet.1 before being driven. If two keys are used in one 
wheel, drive them in gradually and evenly. Driving in one 
key at a time, all the way, will result in throwing the fij-wheel 
iHU and prevent it tnnn running true. Care should be taken 
in strikinir the ends or heads c»f the kevs with a hammer, as 
they may break off if not siruck squarely. 

I: is soir.eiimes found, after placing the wheel on the shaft, 
:liat it ovx^ nm true. This may be due to careless ban- 
v'.V.r.c v.". shi inking or imlvXiding. The damage can be repaired 
..•\: t'x^ \v*u\ '. :r.,u!e :v> rv.r. true by careful hammering of 
s*\^<c> ' oj.r t'^ie r.v.b. Tv^ ascertain which part of the 
n' "v .\:s straic-'or/.r.c t':m it slowly by hand, holding 

lo^e to the rim, thus marking the 

■^ . \ 


higher part of the rim. Then strike the spoke or spokes 
under this part of the rim with the blunt end of a medium- 
sized hammer. To avoid injuring the paint, hold a piece of 
sheet copper against the part of the spoke with which the 
hammer comes in contact, and strike a spot about 2 or 3 inches 
distant from the outside of the hub. 

36. Piston and Connectinfi^-Bod. — The piston and 
connecting-rod are generally shipped detached, and, even 
if they are in position when the engine is received, it is 
advisable to disconnect the rod, take out the piston, and 
thoroughly examine both. Remove all antirust material 
used in packing by washing the surfaces in kerosene and 
rubbing with cotton waste. See that the outer surface of the 
piston is smooth, arid that the edges have not been damaged 
in handling. If necessary, smooth off any slight ridges with 
emery cloth or a very smooth file. The closed end of the 
piston, which is exposed to the combustion, must be smooth 
and must not show any imperfections in the casting, such as 
blowholes or sandholes. Defects of this nature may easily 
cause premature ignition of the charge. 

The piston rings should move easily in their grooves, with- 
out, however, any lateral play. If they stick, use kerosene 
freely, until any gummy oil or material has been washed 
away. If the piston pin that holds the piston and connecting- 
rod together is lubricated through a hole in the wall of the 
piston, see that this hole is clean and affords no obstruction 
to the flow of oil to the pin. 

37. Clean both bearings of the connecting-rod, and after 
cleaning aud giving a liberal coat of oil to the piston pin, 
insert it in the piston, with the rod held in place between the 
bosses inside of the piston. The inner walls of the latter 
should be free from any trace of molding sand, turnings, or 
filings that might find their way into the cylinder and cut 
the working surfaces. It is good practice to give the rough 
inner piston surface a coat of black fireproof asphaltum paint 
before the piston is placed in the cylinder. This should prop- 
erly be done by the maker of the engine, but, if neglected, it 


will benefit the purchaser to have it attended to before any 
attempt is made to start the engine. Clean the interior of 
the cylinder and examine the condition of the working 
surface to make sure that it is in perfect condition and 
shows no longitudinal scratches or ridges caused by the cut- 
ting of the piston. 

38. After the piston pin has been inserted, tighten the set- 
screws and locknuts used for holding the pin in place. Apply 
a liberal quantity of cylinder oil to the outer surface of the 
piston, which is now ready to be placed in the cylinder. The 
end of the cylinder nearest the crank-shaft is usually tapered, 
so as to make it from ^ to {^ inch larger in diameter than 
the piston, to facilitate the insertion of the latter into 
the cylinder. The piston rings, being naturally expanded, 
must be compressed so as to enable them to enter the cylin- 
der. In small engines this can be done by hand, while in 
larger pistons, it will be found more convenient to use cord 
or thin flexible wire with which to draw the rings together. 

39. After the piston has completely entered the cylinder, 
move it backwards and forwards several times to ascertain 
whether or not there is any obstruction to prevent it from work- 
ing freely. The cap of the crankpin bearing of the connect- 
ing-rod having been removed, the crank is now turned so as to 
bring the crankpin opposite its bearing, and the rod and 
piston are moved out until the bearing rests against the pin. 
Then put on the connecting-rod cap and tighten the bolts 
until the bearing is properly adjusted. Always use a liberal 
amount of lubricating oil on both pi^ and brasses before 
putting them together. 

40. Valve-Ck^ar Shaft, Valves, and Governing 

Moohanisni. — In most cases either the crank-shaft or the 

scooTularv or cam-shaft is shipped detached from the engine, 
:r^! Tv.iist Iv put in place by the erector. As the time of open- 
i:vc aTul closinvr the inlet and exhaust valves, as well as the 
PvvItu of ivTvition, is detcTmined by the cam-shaft, it is obnous 
that there is a oenain relati\-e position of the gears that drive 



the secondary shaft. These gears may be spiral, spur, or 
bevel gears, but in any case it is necessary that the teeth of 
the gears mesh so as totime the valves and igniter properly. 
This time having been determined at the factory when the 
engine is assembled and tested, the maker generally marks 
the gears by letters, ciphers, or similar marks, one on the 
tooth of the driving gear, and a corresponding mark on the 
space betft'een the teeth of the driven gear. 

41. When placing the shafts in their bearings, be sure 
to look for these marks, and put the gears together so that 
they mesh as intended. The maker of the engine is of course 
supposed to know the exact timing of the valves and igniter 
that will give the best results obtainable with his particular 
engine, considering its design, speed, etc., and no attempt 
should be made by the purchaser or attendant to improve 
,the tengine in this respect. Generally speaking, however, 
the exhaust valve should close at a point when the crank- 
shaft has passed the inner dead center, after the end of 
the exhaust stroke, by from 6° to 10°. The length of the 
cam or other similar device used for operating the exhaust 
valve will then determine the point of opening, which, in an 
engine of moderate speed, will be about 40° to 46° before 
the crank reaches the outer dead center on the working, or 
expansion, stroke. 

The inlet valve, if operated by a cam or a lever, generally 
opens a little before the beginning of the suction stroke, pos- 
sibly 5" to 10', so that for a very short period of time both 
inlet and exhaust valves are open, say during 10" to 20° of 
the crank movement. The inlet valve will generally be found 
to close, when the crank has passed the outer dead center, 
at the end of the suction stroke — to an extent of from 15° to 
30°, dependingon the fuel and other conditions. If operated 
by the partial vacuum inside of the cylinder, created by the 
outward movement of the piston during the suction stroke, 
the inlet valve of course opens and closes automatically, 
and the timing is regulated by the tension of the inlet- 
Wlhie spring. 


42. The timing of the fuel-admission valve, where the 
valve is mechanically operated by cam and lever or some 
similar device, depends on the kind and quality of fuel used, 
and also on the pressure at which it is supplied. With 
illuminating gas at the average pressure, the valve should 
open when the crank has passed the inner dead center about 
15° and close about 30*^ after the crank has passed the 
outer dead center. The same timing of the air-inlet and 
fuel valves will be found to give the best results when using 
gasoline as when using illuminating gas, if the gasoline is 
supplied through a nozzle controlled by a small popppt valve 
actuated by cam and lever. 

43. As natural gas is much superior to illuminating gas in 
heating value, a differently proportioned mixture is required, 
which is usually regulated by throttling the gas-cock on the 
engine so as to suit the quality of the fuel available. The 
timing of the fuel valve is the same, however, as when using 
illuminating gas. But the poorer qualities of gas, such as 
producer gas or fuel of correspondingly lower heating value, 
require a longer period of time during which the gas valve 
must be open. Generally, it will be found that, in order to 
get good results, the valve must begin to open at about 15° 
before the crank passes the inner dead center, previous to 
the suction stroke, and remain open until the crank has 
passed the outer dead center about 40°. As stated before, 
these angles are only approximate, and they vary slightly 
according to the design of the engine, the area of the valves, 
and the speed at which the engine is operated. 

44. After the cam-gear shaft has been properly placed 
and secured in its bearings, turn the engine over slowly and 
see that the shaft and the parts actuated by it move freely. 
Attach any levers, links, o^ rods that may not be in place 
when the engine is taken from the boxes, lubricating all 
pins and pivots carefully before putting them together. See 
that any valves closed by springs come to their seats quickly 
if pushed in by hand and released. Apply a liberal amount 
of kerosene to all valve stems, so as to remove any gummy 


or similar matter with which they may have become coated. 
Give special attention to the governor, on whose free move- 
ment depends the regularity of speed of the engine. All 
links and pivots connected with the governing mechanism 
should be washed with kerosene and then lubricated with a 
light oil of good quality. 

45. Attacliment of Xiubrlcators. — Before attaching 
the lubricators furnished for oiling the cylinder, bearings, and 
principal moving parts of the engine, the oil cups should be 
carefully examined for any dust or other impurities that they 
may contain. See that they are perfectly cleaned before 
they are put in place and filled with oil. 

The tapped holes for receiving the individual oil cups and 
the holes through which the oil is supplied ta the parts to be 
lubricated should also be examined with great care, and any 
waste or similar obstructions that would tend to interfere 
with the supply of oil should be removed. 


46. Battery and Spark Coll. — The matter of installing 
the battery, spark coil, switch, and wire connection deserves 
the most careful attention. The battery cells should be 
charged and the wire connections between the battery and 
the engine made according to the instructions sent with 
the particular make of battery used in connection with the 
engine to be installed. As a matter of fact, the larger part of 
the trouble with internal-combustion engines is due to the 
igniter and its connections. Some of these difficulties will 
occur if every possible care is taken, but most complaints 
can be traced to neglect or carelessness in installation or 
ignorance in operation. 

As the make-and-break contact system is used almost 
exclusively on stationary engfines, only this method will 
be considered at present. A good quality of insulated fire- 
proof and weatherproof copper wire should be used to con- 
nect the individual cells of the battery and the spark coil 


with the battery and engine. Flexible rubber-covered or 
stranded wire is also permissible. In fastening the wires to 
the ceiling or walls, do not use metal clamps, which are liable 
to injure the insulating material, but use wooden or fiber 
cleats cut out to suit the thickness of the wire. Avoid splic- 
ing whenever possible; but, if it is necessary to employ 
splices, make them carefully and solder them securely. The 
wire should be of such length as to reach from 6 to 9 inches 
beyond the binding post to which it is to be connected. To 
avoid any pulling on the wire or post, the extra length should 
be coiled on a ^ inch round rod, slipped off, and left as a 
spiral between the straight wire and the binding post 

47. Electrical Connections. — The spark coil must be 
set in a dry place and must be well protected from moisture, 
which causes short-circuiting and prevents ignition. All 
terminals of the wire connections must be clean and bright, 
to insure good contact The connections between the cells 
should preferably consist of fle^tible insulated wire, with flat 
Clipper washers soldered to the ends, the hole in the washer 
fitting easily on the binding post Connections of this kind 
may be purchased from almost any electrical supply dealer, 
if they are not already furnished with the engine. 

As a rule, an ordinary two-pole, or two-point, switch, 
with loYor-handle contact will answer all purposes. These 
switches ha\-e the advantage of being easily examined and 
kept in orvicn Knife switches are equally well adapted for 
\i5?c in engine rvx^ms^ while if the switch is necessarily 
ox*jXvv\l tv^ out-ofndoor atmosphere an encloGed switch, such 
as is u:x\l tor iucAnviosoent lights, is more suitable. 

4S, lirnltlon PUur. — The ignition plug containing the 
e\v:rvxU^s '.v.r.s: bo oxani:t^ed as to deanKness, freedom from 
vvrTv>s:on» cs:xv:A!'y v^f tbe cor.ract points* and easy move- 
•*^ov.: v>f tVo n*.o\Vib!o e!tvtTvv5e. befo^re being attached to 
•/*v^ vV.vbusti.^" o^.v^^iSl^t AV>.r.e :be engine is at work, the 
\v ;;, N^ -^C i\iv\^v. :.^ t'^e ht,-.: ?f the combustion, will 
o\a;'*/ s' c^'*'^" •"> "v :'''*,i-*. :'"'c <*,:rrr^niinc waZTs. It is evi- 



in case of necessity, after the engine has been running for 
some time, it must, when cold, enter its aperture easily and 
witliout having to be forced. The packing surface of the 
ping, making it tight against tlie pressure in tlie cylinder, is 
a ground joint, either flat or tapering, or a flat ring-shaped 
surface packed w-ith sheet asbestos. In either case, thepack- 
ingsurfaces must be thoroughly cleaned before the plug is put 
in place anti tightened up, 

49. Point of IgDltlon. — The point of ignition varies in 
accordance with the quality of the fuel and the speed of the 
engine. At medium speed, whea using iUuminaiing gas or 
gasoline, the ignition should occur just before the end of the 
compression stroke, with the crank standing at about 15" to 
20" below the inner dead center. Natural gas, as well as 
producer gas, the combustion of which is somewhat more 
sluggish, requires a diflferent timing of the igniter, and the 
spark should occur when the crank stands about Z'i" to 35° 
below the inner dead center. 

50. Testing: the Eleetrlcal Connections. — The testing 

of ibeelectrical connectionsmay be said tocomplete the instal- 
lation of the engine and put it in condition for starting. To 
determine whether the wires transmit the current in the 
proper manner, connect the battery, spark coil, switch, and 
engine as directed. Then disconnect the terminal attached 
to the fixed electrode, turn the engine to such a position that 
the two electrodes will be in contact, see that the switch is 
turned on, and wipe the end of the wire against the surface 
of the nut that holds the fixed electrode in place. If every- 
thing is in good order, a bright spark will then be produced. 
On the other hand, after turning the engine so that the con- 
tact between the two electrodes is broken, no spark should 
appear when the fixed electrode is touched and wiped in this 
manner; in wiping any other bright part of the engine, how- 
ever, a spark of similar intensity to that just referred to 
1 be produced. 




61. Adjustment of liUbricators. — After the engine 
has been assembled and connected, the oil cup should be 
filled and tested to ascertain that the feeds work properly. 
The adjustment of the cups should at first be such as to sup- 
ply a rather liberal number of drops; later, the quantity of 
oil may be cut down to the normal amoimt, after it has been 
demonstrated that the bearings nm cool. In a vertical 
engine using splash lubrication, fill the oil well in the base 
until the ends of the connecting-rod bolts dip about \ inch 
into the oil when the crank stands at its lowest point Make 
sure that all links, levers, and pivots have been lubricated, 
that the valves and igniter move freely, and that the water 
supply, if taken from the mains, is circulating properly. 

To make certain that the crankpin and the piston pin are 
properly lubricated before starting, apply a small quantity 
of oil to each by hand, without relying on the lubricator or 
mechanical oiler provided for the purpose of oiling these 
parts while the engine is running. Sometimes these devices 
may fail to perform their functions as promptly as is neces- 
sary, and a hot bearing may result, causing serious trouble 
that could have been easily avoided by taking this simple 

52. The oil wells of the ring-oiling bearings should be 
filled to the proper height, and it should be ascertained that 
the oil ring or chain moves freely, so that it will distribute 
the oil over the journal surface when the shaft revolves. 
Wiper oilers must be adjusted so that the moving element 
of the de\ice touches the stationary part of the oil cup only 
lig^htly enough to wipe off any drops of oil suspended fr<jni 
the metal tip or wick of the feeding dexice. If the wiper 
scrapes too hard against the tip of the cup, it will waste oil 
and throw it over the encrine. 


Worm or spiral gears, which are often employed to trans- 
mit motion from the crank to the cam-shaft, are usually run 
in an oil bath. The casing containing these gears must 
therefore be filled with oil before starting. 

53. Examination of Piston. — Examine the way in 
which the piston works in the cylinder. A proper fit of the 
piston is of the utmost importance, in order to obtain good 
service from the engine. It must move freely, but at the 
same time must prevent any loss of pressure during 
the compression and expansion strokes. When turning the 
engine by hand, there must be no hissing sound during 
the compression; this would surely indicate a defective piston 
or improperly fitted piston rings. A perfectly fitted piston, 
tried in this way, will rebound before the end of the com- 
pression stroke is reached. 

54. Examination of Valves and Igniter, — If the 

engine can be turned over easily through the compression 
stroke, it will be difficult or impossible to start it. The 
loss of pressure, however, which prevents proper com- 
pression, is not likely to be due to an imperfect piston, 
especially in a new engine, but rather to a valve that leaks 
or to leakage about the movable electrode. It is well, there- 
fore, to ascertain the cause of such a leak, by thoroughly 
examining the inlet and exhaust valves and the igniter. 
Possibly one of the valve stems or the electrode may stick in 
the guide, or there may be an obstruction on one of the 
valve seats. Where packings are used, one of them may 
have been damaged or partly blown out. 

An application of kerosene to the valve stem will wash 
away any thick oil, grease, or similar substance that may 
cause the valve to stick. If impurities have been deposited 
on the valve seat, they can usually be removed by lifting the 
valve by hand and cleaning the seat with a scraper or some 
similar tool. In the case of larger valves seated in casings too 
heavy to be handled conveniently, the valve may have to be 
taken out before the seat can be examined and cleaned. 

The renewal of a packing, especially when the packing 


surface is of considerable size, is a more serious matter, and 
should not be undertaken until a careful examination has 
shown the necessity for doing so. 

56. Adjustment of Igrnition Device. — ^Where an incan- 
descent metal tube is used for igniting the charge, this tube 
must be brought to its proper temperature before the engine 
can be started. The heating devices used in connection with 
these tubes differ according to the fuel employed. In any 
case, however, whether the fuel is gas or gasoline, the 
burner must be so adjusted that a sufficient quantity of air 
is supplied to obtain a hot blue flame. A yellow flame 
indicates a lack of air. The degree to which the tube is 
heated not only influences the point of ignition but also has 
a material effect on the life of the tube. 

Iron tubes, while less expensive, do not last so long as 
tubes made from special nickel 'alloys; but, in either case, 
the life of the tube is shortened by overheating. This will 
readily be understood when it is remembered that overheat- 
ing causes the tube to become soft, in which condition it can- 
not resist for any length of time the high explosive pressure, 
which has a tendency to burst the tube. Generally, the 
most favorable condition in regard to the proper timing of 
the ignition and the longest possible service is reached if the 
tube is heated to a bright cherry red. 

The preparation of electric-ignition devices previous to 
starting the engine has already been explained. The engine 
having been properly assembled and connected, the lubrica- 
tion having been attended to, the valves moving freely and 
seating tightly, and the means of igniting the charge being 
in good working order, the engine may be considered ready 
for starting. 

56. Means of Starting:. — Small engines are often 
started by hand, simply requiring the opening of the fuel 
cock and the turning of the flywheel until the charge thus 
admitted is ignited, giving the engine an impulse sufficient 
to carry it over the following strokes of its cycle until sub- 
sequent charges are admitted and ignited. In this manner, 


the engine reaches its full speed when from ten to twenty 
explosions have taken place, the number of explosions 
depending on the weight of the flywheeL An engine 
equipped with heavy wheels requires, naturally, more 
impulses before attaining full speed than one with light 

57. Dlfflcnlties In Startlngr- — Difficulties in starting 
usually met with in practice may be due to various causes. 
Above all, it must not be supposed that an engine that has 
nm regularly for a period of time will refuse to run without 
cause, and the origin of the trouble should be located as 
speedily as practicable. The most common sources of trouble 
in starting are improper proportion of the constituent parts 
of the mixture, failure of the igniter and its connections, or 
loss of pressure during the compression and expansion 
strokes. A proper proportion of air and fuel is of great impor- 
tance to prompt and effective combustion. It should be 
remembered that when starting by hand, with the piston 
moving slowly, the fuel valve remains open for a longer 
period of actual time than when the engine is running at its 
normal speed. The fuel being usually supplied under a cer- 
tain amount of pressure, while the air is drawn from the 
atmosphere, it follows that, with the engine turning slowly, 
the proportion of fuel to air is greater under these condi- 
tions than under normal working conditions. This condition 
is made still worse when the inlet valve is of the auto- 
matic type, being opened by the partial vacuum created in 
the combustion chamber by the outward movement of the 

58. Befiralation of Mixture In Starting^. — In order 
that the quantities of air and fuel may be regulated so as 
to admit a mixture of the proper quality, the fuel cock 
should be only partly opened during starting. The cock or 
throttle being usually fitted with a graduated dial, the opera- 
tor will be able after a few trials to determine at which 
point of opening the engine will start readily. When using 
illuminating gas, this point will vary in accordance with 


fluctuations in pressure that may occur at different times of 
the day. 

A common mistake made by inexperienced operators is to 
admit too much fuel to begin with, and if the engine natur- 
ally fails to ignite, to still further open the fuel cock and 
thus aggravate the trouble. This applies equally well to 
gaseous and to liquid fuels. As a result of opening the fuel 
supply too wide, the combustion chamber becomes flooded 
with gas or vapor, and conditions are not improved until 
the supply has been shut off completely and the engine 
turned over several times, so that the contents of the cylin- 
der are expelled through the exhaust pipe. 

69. When operated with illuminating gas, it \^'ill gen- 
erally be found necessary to first open the valve in the pipe 
back of the gas bag, let the bag become inflated, then shut 
off the valve, and start the engine on the pressure exerted 
by the gas contained in the bag and pipe between it and • 
the engine. As soon as the bag shows signs of becoming 
empty, which will occur after a few explosions, the fuel cock 
must of course be opened. 

When using gasoline, the air can vaporize only a certain 
quantity of fuel. Any excess will be deposited and will 
accumulate in the inlet passages and in the combustion 
chamber, and the longer the wheels are turned with this 
excessive opening of the fuel supply, the more aggravated 
will the trouble become. Frequently, if under these con- 
ditions the fuel supply is shut off completely and the turn- 
ing of the wheels continued, an explosion will occur as soon 
as the amount of fuel carried into the cylinder is reduced to 
the point when a properly constituted mixture is formed. 

60. In a well-designed engine, the fuel cock is propor- 
tioned so that it must be opened full, in order to obtain a 
perfect mixture %vith the engine running at full speed. 
Engines with air-inlet valves positively operated by means 
of cams and levers are less liable to failure in starting 
caused by improper proportions of the mixture. This is due 
to the fact that in such engines the air-inlet valve and the 


fuel valve are open during the same period of time, thus 
regulating to a certain extent the quantities of air and fuel 
forming the charge. 

61. In engines operated on liquid fuel, such as gasoline, 
kerosene, etc. , the fuel must be pumped by hand until a 
sufficient quantity is raised from the supply tank to the 
level of the fuel-admission valve to start the engine. The 
fuel is generally pumped into a small cup provided with an 
overflow pipe, which returns to the supply tank any excess 
amount of fuel over that which fills the cup to a certain 
level. This cup and overflow device may be a part of the 
fuel valve or it may be separate. 

When first starting the engine, it may require quite a 
number of strokes of the fuel pump before the air in the 
suction pipe between the tank and engine is pumped out and 
the liquid delivered to the valve. If there is difficulty in 
pumping the fuel, it is a sure sign of leakage of air in the 
supply pipe; if the liquid does not stay in the cup after 
being pumped up, it indicates tljat there is leakage at some 
point between the cup and the engine. Before attempting 
to run the engine, therefore, the pipes and connections 
should be carefully examined, the leak located, and any 
imperfect joints made tight. 

63. In the modern gasoline engine, a mechanically 
operated device, which determines the exact amount of fuel 
sprayed into the air, atomizes the gasoline while entering 
the mixing chamber at a certain velocity. It is therefore 
evident that the forming of a proper mixture and the conse- 
quent prompt starting are not dependent on atmospheric 
conditions and quality of the fuel to the same degree as 
when the old type of vaporizer was used. Nevertheless. 
in extremely severe weather, in locations where the engine 
room is not kept warm during the night, and especially 
when the fuel used is of comparatively low specific gravity, 
it may become necessary to aid the atomizing of the gaso- 
line by heating the combustion chamber in some manner 
before starting can be attempted. 


The fuel is sometimes heated by removing the inlet- or 
exhaust-valve cover and placing a quantity of cotton waste 
soaked in kerosene in the combustion space and lighting the 
waste, but this is a crude and dangerous proceeding and 
cannot be recommended. In 'addition to the danger con- 
nected with an open flame, the burning of waste may easily 
result in leaving in the chamber fragments of the material, 
which may be drawn into the cylinder and interfere wnth 
the proper working of the piston, valves, and igniter. An 
absolutely safe way of accomplishing the desired object is to 
fill the empty water space in the jacket with hot water pre- 
pared for this purpose. This will increase the temperature 
of the walls surrounding the combustion chamber sufficiently 
to aid in the vaporization of the fuel and make prompt start- 
ing more certain. 

63. No set rules can be laid down that will tell the opera- 
tor just how to obtain a perfect mixture at all times. 
This depends on the design of the engine and on the condi- 
tions surrounding each individual case, which may necessitate 
a different method from that which must be observed in 
another engine of the same type or make. Indications of a 
good mixture will manifest themselves to an observant 
operator by the sound of the impulse and the appearance of the 
exhaust at the end of the exhaust pipe. A smoky exhaust is 
a certain sign of an excessive amount of fuel, and a mixture 
of this kind also produces a weak impulse. If the exhaust is 
clear and it requires the admission of several charges in suc- 
cession before an explosion occurs, the indications are that 
the fuel is not admitted in sufficient quantity. This condi- 
tion also manifests itself by back flringr or explosions in 
the air pipe and passage, caused by retarded combustion of 
the charge, the mixture being still burning at the end of the 
exliaust stroke and igniting the incoming charge while the 
inlet valve is still open. 

04. RepTulating Gas Pressure. — Engines operated 
with illuminating or natural gas require the same amount of 
judgment in determining the amount of fuel to be admitted 



vrhile startinff the engine as does a gasoline engine. If 
illuminating gas is used, the pressure is regulated at the 
gasworks, and any slight fluctuations are equalized by use 
of a rubher bag, as already explained. When running with 
natural gas or pnxiucer gas, the pressure is frequently regu- 
lated by a small gasometer, as illustrated in Fig. 8, consist- 

JDg of a tank a partly filled with water in which is sub- 
merged a float b, closed at the top and open at the bottom. 
The gas-supply pipe c from the main enters the gasometer 
at the bottom and extends through the watpr into the float, 
while the pipe d connecting the gasometer to the engine is 
attached in a similar manner. The float b is connected to 
the valve cva. the supply pipe in such a manner that, when 
the float becomes filled with gas, it rises and closes the 
valve e. As 80<m as the engine takes a charge of gas from 


the gasometer, the float b descends, and in doing so opens 
the valve e far enough to replace the amount of gas con- 
sumed by the engine. According to the existing conditions, 
the pressure exerted by the weight of the float may be 
increased by placing weights on top. The operator will 
learn by experience just how far the dial cock on the engine 
must be opened to make prompt starting possible. 

65. Timing the Igrnitlon. — A very important feature 
to be observed in starting an engine is the proper timing of 
the igniting device. This of course applies more particu- 
larly to electric ignition, as the hot-tube method is generally 
automatic in its action and is not timed by any mechanical 
device, but depends, for firing the charge at the proper 
moment, on the diameter and length of the tube and the 
temperature to which it is heated. Electric igniters are 
almost universally equipped with a retarding device that 
allows the breaking of the contact between the two elec- 
trodes and the resulting spark to occur after the crank-shaft 
has passed the dead center at the end of the compression 
stroke and to thus prevent the engine from turning back- 
wards suddenlv while the flvwheels are beincf turned bv 
hand. It is therefore necessary to be sure that the igniter 
lias been set in starting position, to avoid possible injury to 
the operator. To lessen the liability to accident in case of 
unexix^cted reversing of the engine while starting, it is 
advisiible to avoid placing the foot on the flywheel spokes 
when turning it by hand. If the engine is properly lubri- 
cated, and the relief valve generally provided for the escape 
ot a part of the compression pressure during starting is 
working properly, it is always possible to turn an engine up 
\o ;>(> horsepower by hand without putting the foot on the 


66. This prt^caution in timing the point of ignition 
a:^v:iv s to electric i'^nition K^i the make-and-break contact as 
we'l .IS t'e iump-spark methvxi. In the latter case, the 
t-Tv.i-:^ vievicc. w'^ich n.\ctilates the moment of ignition, be aviiusteJ so as to make the spark suflSciently late to 


prevent reversing of the engine; hence a plainly visible 
mark of some kind should be provided that will tell the 
operator just how the timer must be set 

In case of failure to ignite, first see that the vibrator of 
the coil is working properly when the current is on. Also 
detach the wire connected to the plug, and test the distance 
the spark will jump by holding it close to any metal part of 
the engine. In doing this, it must be remembered that a 
spark will not jump as far when exposed to the high-com- 
pression pressure in the cylinder as it will in the open air. 
It should therefore be capable of jumping a gap of about 
y\ to ^ inch when tested on the outside of the cylinder. 

If the spark is found to be satisfactory, take out the plug 
and examine the ends of the platinum wires, removing any 
carbon deposit or other impurities that may have accumula- 
ted there. Also see that the insulators are' in good order, 
that they have not been cracked, and are free from grease ; 
if necessary, cleanse them by washing with gasoline before 
putting them back in the plug. 



67. In order to insure reliable service, an engfine should 
be given the necessary care regularly. Those parts that con- 
tribute principally to the proper operation of the engine, such 
as the igniter, valves, governor, bearings, and lubricators 
should be inspected at regular intervals. 


68. Under ordinary conditions of service, when running 
about 10 hours a day, the igniter should be taken out once a 
week, the contact points examined, and, if necessary, cleaned 
or dressed. There must be no leak past the seat of the 


movable electrode, and as soon as any leak occurs at tMs 
point, as indicated by a hissing sound, the electrode must 
be taken out and ground to a perfect seat with fine emery 
powder and oiL 

The stationary electrode is usually insulated with mica, 
porcelain, or lava washers or bushings, and packed with 
asbestos, so as to make it tight against the pressure of the 
explosion. If the packing of this electrode is damaged, 
the steel pin itself will be exposed to the intense heat of the 
burning charge. A gas leak will appear around the pin, and 
when trying to overcome this by tightening the nut at the end 
of the pin, the heated steel will be reduced in size. If this is 
repeated a few times, the pin will soon be useless. It is evi- 
dent, therefore, that the fixed electrode must receive particu- 
lar care in regard to preserving perfect insulation and tight 
packing. Mica insulators are probably best, as they are not 
liable to cause short circuits and consequent interruption of 
the service, by cracking, to which porcelain or lava bushings 
are subject. They also have the advantage of being suffi- 
ciently pliable not to require any asbestos washers to make 
them tight. 


69. There should always be a clearance of about -^ inch 
between the end of the valve stem and the lever operating it, 
so as to make certain that the valve can come to its seat, 
even after it has become expanded by the heat while in 
operation. Repeated grinding will reduce the amount of 
clearance, and adjustment must be made by slightly with- 
drawing the setscrew usually provided in the end of the 

Inlet valves are naturally kept more or less cool and clean 
by the incoming mixture, and require grinding less frequently 
than exhaust valves. Inspection and thorough cleaning 
once a month, however, are advisable. Automatic inlet 
valves, opened by the suction during the outward stroke of the 
piston, must move freely in their guides; any deposit of 


carbon or gummy oil will tend to interfere With their proper 
working. Kerosene applied to all valve stems at regular 
intervals will aid in keeping the stem clean and prevent it 
from sticking. The nuts and lock nuts on the end of the 
valve stem, which keep the spring in place, must be kept 
tight Carelessness in this matter may cause the valve to be 
drawn into the combustion chamber, where it may cause 
serious damage to the cylinder or piston. 

70. If the inlet valve is operated by cam and lever, the 
same precaution as to a small amount of clearance between 
the end of the stem and the lever must be observed, as 
referred to in connection with the exhaust- valve stem. The 
inlet- valve casing usually has in the cylinder head a ground 
joint that requires the same care as the valve seat. 

When using gas, the fuel valve operates under much the 
same conditions as the inlet valve just referred to. The 
same directions for cleaning and adjusting will therefore 
apply to this valve. Gasoline poppet valves are often fitted 
with small stuflSngboxes packed with wick saturated in a 
mixture of soft soap and graphite powder. Care should be 
taken to keep the stuffingboxes tight enough to prevent any 
leakage of gasoline past their stems, but not so tight as to 
prevent the springs from closing the valves promptly. It 
will be found that a brass gasoline-valve stem will ^ve bet- 
ter service than a steel stem, as the packing material has a 
tendency to cause the latter to rust and stick. 


71. The gas-cock, or throttle valve, generally consists 
of a cast-iron casing, a brass plug, and a graduated dial, with a 
handle to open and shut the cock. In order to be able to 
move the plug easily, it should be lubricated occasionally 
with a thin coat of oil and graphite. The screws that fasten 
the dial to the body of the throttle valve and hold the plug 
in position must be tightened evenly, so as to avoid leakage 
of gas at this point. When using natural or producer gas. 


which is usually not so pure as illuminating gas, it will be 
found necessary to clean the gas-cock, as well as the gas- 
valve stem and casing, more often. Kerosene will be f otmd 
useful for this purpose. 


73. Owing to the fact that gasoline vaporizes easily, it 
is more difficult to lift it by means of a pump than it is to 
lift water. The condition of the gasoline pump is there- 
fore of great importance in getting good results from a gaso- 
line engine. The plunger must be packed well with suitable 
material. Lamp wick or asbestos wick thoroughly saturated 
with a mixture of soft soap and graphite has proved an excel- 
lent packing for the stuffingbox of the gasoline pump. The 
valves, whether they are standard-type check-valves or flat- 
seated valves fitted with leather washers, must be kept free 
from impurities that may lodge on the valve seats and cause 
the pump to become air-bound, when it will naturally refuse 
to work. Filters used in the gasoline supply pipe, before it 
enters the pump, must be taken apart occasionally, and any 
impurities that may have gathered there must be removed, 
so as to afford a free passage to the fuel. 


73. A steady speed is largely dependent on the working 
of the governor and its attachments. TO insure good results 
in this respect, the levers and links of the governor must 
work freely, and at the same time there must be no lost 
motion in any of these parts. A thin lubricating oil should 
be used on all governor parts, and at regular intervals the 
whole governor should be taken apart, its pivots, levers, eta, 
cleaned by washing with kerosene or gasoline, and put 
together again after applying a liberal amount of lubricating 
oil. In most engines, the speed is adjusted by the tension 
of the governor springs, a higher speed being obtained by 
increasing, and a slower speed by decreasing, the tension of 



the springs. It is not advisable to increase the speed of an 
engine beyond the normal number of revolutions without first 
consulting the manufacturer. 


74. Self-Starters.^To obviate turning the flywheels 
by hand, which in engines of the larger size would be incon- 
venient, if not impossible, most builders equip engines of more 
than 40 horsepower, and sonaetimes even smaller sizes, with 
self-starting devices, consisting of hand pumps for compress- 
ing the explosive mixtures in the combustion chamber, and 
detonators or sparking devices for firing these charges by 

In a gasoline engine, the charging pump is usually 
attached to the aide of the cylinder and is fitted with a small 
receptacle at the top or bottom containing a quantity of gaso- 
line, over which the air is drawn before being forced by the 
pomp into the cylinder. The air valve is automatic, and is 
held to its seat by means of a spring, the tension of which 
limits the lift of the valve and the amount of air pumped 
into the cylinder. 

The charging pump of a gas engine takes the fuel from 
a small pipe connected to the gas supply, the gas being 
mixed with air while entering the pump cylinder through a 
series of email holes in the seat of the inlet poppet valve. 
Before charging the cylinder, the detonator, if one is used, 
must be charged with a parlor match, a portion of tlie 
wood being removed so that only the head end is inserted in 
the end of the detonator. 

7S. In order to start the engine properly, it must be 
turned until the beginning of the working or expansion 
stroke is reached. At this point of the cycle, the engine has 
just completed the compression stroke and the exhaust cam 
is about 180° away from the roller that operates the exhaust 
Valve, With the crank in this position, the mixture is 
ftffced into the cylinder by giving a few quick strokes with 


smaller number of drops than when full, and it is therefore 
well to always keep them filled. The temperature of the 
engine room also has some eflfect on the rate of feed, and 
in very cold weather the oil should be warmed before pour- 
ing it into the lubricators. 

Force-feed lubricators supplying oil through tubes to the 
various bearings are more positive in their action in regard 
to the quantity supplied under varying conditions. Care 
should be taken, however, to guard against waste or other 
impurities settling in the bottom of the reservoir, whence 
they may easily be carried into the oil pipes and interfere 
with the free flow of oil to the parts to be lubricated. 

80. licvel of Oil In €rank-€ase. — In engines using 
the splash method of lubrication the level of the oil in the 
crank-case should be maintained at a uniform height, as 
indicated by the gauge glass usually provided. While it is 
necessary to keep the oil level sufficiently high to insure 
good lubrication, it is equally important not to allow it to 
become too high, because in that case the surplus oil is car- 
ried past the piston, and is not only wasted but becomes a 
source of trouble by depositing itself on the igniter points 
and causing them to work irregularly. It may be observed, 
however, that the fitting of each individual cylinder and 
piston has some effect on the amount of oil thus carried into 
the combustion chamber. It will therefore be found that 
the oil level that must be maintained in order to get suffi- 
cient lubrication of the piston may vary in two engines of 
the same make and size, and in all cases great caution 
should be exercised to carry the oil up to such a level that 
there will be no doubt about sufficient lubrication. After 
the proper level has once been determined by experience, 
the oil gauge should be marked, so as to show at a glance 
whether the oil is up to the required height. 

81, Pressure In Crank-Case. — In some vertical four- 
cycle engines that use the splash system of lubrication, the 
escape of oil past the main bearings, due to the pressure 




produced by the movement of the piston, is guarded against by 
the use of a check-valve, a sectional view of which is shown 
ia Fig. 9. The valve casing is attached to the crank-case, 
and the valve a is made adjustable, the tension of the 
springs b and c being 
varied so that the valve 
jost closes the port d 
communicating with the 
crank-case when the en- 
gine is not running. 
When the engine piston 
moves downwards, the 
increase in pressure in the 
crank-caseopens the valve, 
affording a relief for the 
surplus pressure On the 
upward stroke of the pis- 
ton, the partial vacuum 
closes the valve and pre 
vents any air from being 
drawn in. 

82. Benewlnsr the 

Oil. — The oil m the crank 
case should ne\er be left "^' 

more than a wtek without inspection Generally, it will 
have become thick and unht for use by that time and should 
be removed. If tliere is a leak of exhaust gases past the 
piston, the oil in the crank-case will mix with the water from 
the gases and may become charged with acid from the sul- 
phur that is present in these gases. This must be prevented, 
as the acid will gradually corrode and pit the journals of the 
crank-shaft asd other moving parts with which it cornea in 



83« To avoid mistakes or oversights in starting, caring 
for, and stopping engines, the operator should adhere to a 
certain routine while performing his duties. The following 
rules in regard to the order in which the various operations 
in starting and stopping should be performed may prove of 


84. 1. Attend to all lubricators and oil holes, always 
following the same order. 

2. Apply a few drops of kerosene to the valve 

3. Open the gas-cock back of the rubber bag or regula- 
tor, or, when using gasoline, open the cock near the tank, 
and work the gasoline pump by hand tmtil the liquid 
appears in the valve or overflow cup. 

4. See that the electric igniter is properly connected; 
turn on the switch and see that the spark is of proper inten- 
sity; or, in case of tube ignition, light the burner that 
heats the tube. 

5. Turn the flywheel until the engine is at the beginning 
of the working stroke. 

6. Open the fuel cock to the point that has been found 
most reliable for starting. 

7. Throw the relief cam in gear or open the relief 

8. If a compressed air or some other self-starter is 
employed, operate the device in accordance with the instruc- 
tions given in pre\ious paragraphs relating to this style of 
apparatus. If no starting devices are used, turn the fly- 
wheels rapidly imtil the engine starts. 

9. Close the relief valve or disengage the relief cam and 
open t::e fuel ctx^k to its full extent, gradually, as the speed 
of the e:iiri-<^ increases, 

1«\ Tv.rr. o'l :;ie cvH.«'iir.Lr water, it running water is used, 


or see that the tank is full and the cocks open if the tank 
system of cooling is employed. 

11. Throw in the friction clutch or shift the belt to the 
tight pulley on the line shaft. 


85. 1. Disengage the friction clutch or shift the belt to 
the loose pulley on the line shaft. 

2. Close the gas-cock near the rubber bag or regulator, 
or the gasoline cock near the storage tank. 

3. Close the gas or gasoline cock on the engine. 

4. Throw off the switch between the battery and the 
engine, or turn off th^ burner that heats the tube. 

5. Drain the water-jacket by closing the valve in the 
supply pipe and opening the cock that connects the bottom 
of the cylinder to the drain pipe. If water tanks are used, 
close the cocks in the water pipe and open the drain cock. 

6. Shut off all sight-feed lubricators. 

7. Clean the engine thoroughly, wiping off any oil or 
dust that may have accumulated on the engine. 

8. See that the engine stops in a position where exhaust 
and inlet valves are closed. If necessary, turii the wheels 
by hand until this position is reached. It will protect the 
valve seats against corrosion. 


k < 


■ J 


^ -^ 







1. Defective action is sometimes due to causes so appar- 
ent that explanations are unnecessary; hence, for the sake of 
convenience, all these possible sources of trouble have been 
grouped tmder the headings Causes of Refusal to Start, 
Causes of Misfiring, and Causes of Weak Explosions. 
In each case, the cause of the trouble may generally be 
traced in the last analysis to faulty ignition, a faulty mix- 
ture, or an insufficient supply of mixture. These broad, 
ultimate causes have been stated first, and the principal 
mechanical or electrical defects that produce the trouble are 
enumerated afterwards. It will be understood that these 
do not comprise all the possible troubles with engines. In 
particular, they omit entirely such matters as preignition, 
knocking, and overheating. The object of the following 
presentation is to enable the user to trace the difficulty 
when his engine refuses to give its normal power through 
some trouble, the nature of which is not immediately 

3. It is a familiar fact that the internal-combustion 
engine is far more liable to stoppages and weaknesses, for 
reasons at first mysterious, than is the steam engine. The 

QffytigkUdiaf JmUrmaUamai Textbook Company, Entered at Stationer fHali^ London. 



explanation of this is that, while the steam engine is purely 
a mechanical apparatus, the internal-combustion engine is 
partly mechanical, partly chemical, and generally partly 
electrical in its functions, and the chemical and electrical 
parts of its organism may go wrong through causes not con- 
nected with the visible mechanism, or — as in the case of a 
badly adjusted trembler, a poorly working timer, or a leaky 
float — through mechanical derangements so slight as to 
escape notice. 

From this it follows that, to manage successfully, an 
internal-combustion engine— especially one that works under 
such a variety of conditions, often very severe,. as the auto- 
mobile engine — it is first o^all necessary for the operator to 
make good use of his reasoning faculties. The symptoms of 
derangement, when taken singly, are often such as may 
be caused by any one of several possible defects; in nearly 
every case the defect, whatever it may be, will produce 
several S)rmptoms a careful study of which will lead to the 
elimination of causes that do not tally with all the symp- 
toms ; as, for instance, causes affecting all cylinders when 
only one or two are misbehaving, or vice versa. When the 
user has reached this point, generally a short further inves- 
tigation of the points at which he has found trouble of that 
particular sirt is most likely to occur will lead him to the 
discovery of the true cause. The cause of loss of power, due 
to such faults as a loose battery connection, a sticking inlet 
valve, or a bit of dirt in the carbureter, will at once be recog- 
nized in its true character by the experienced operator. The 
only way to attain final proficiency in these things is by 
extended experience with the particular engine in hand; but, 
on the other hand, there is absolutely no excuse for the aim- 
less groping of many inexperienced users, who will often 
send needlessly for a tow, or will pull an engine to pieces in 
their search for some simple fault that might have been 
located by intelligent diagnosis. 

3, Causes of Refusal to Start, or of Sudden Stop- 
pag:e. — The fundamental reasons for an engine refusing to 



run, or of a particular cylinder refusing to work, may be 
summed up as due to (1) no spark; (2) no mixture; or (3) 
wholly wrong mixture. These cover all the possible causes, 
which may be enumerated as follows : 

1. Switch not closed. 

2. Gasoline not turned on. 

3. Carbureter not primed, or (rarely) primed too much. 

4. Weak battery. 

5. Gasoline stale or mixed with kerosene. 

6. Gasoline too cold to vaporize. 

7. Dirt or waste in carbureter or gasoline pipe. 

8. Mud splashed into air intake. 

9. Water in carbureter. 

10. Soot on the spark plug or contact igniter. 

11. Water on spark plugs. 

12. Broken spark-plug porcelain. 

13. Grounded wire (generally secondary). 

14. Broken wire (generally primary), or loose connection. 

15. Very bad adjustment of *the coil tremblers. 

16. Defective spark coil or condenser (rare). 

17. Broken igniter spring. 

18. Broken valve stem, spring, or key. 

19. Valve cams slipped (rare). 

4. Causes of Misfiring:, — The principal cause of mis- 
firing is irregular sparking, which may be due to a variety 
of causes. Irregular sparking may be caused by the 

1. Soot on spark plugs or contact igniters. 

2. Weak battery. 

3. Broken wire, making intermittent contact through 
the vibration of the car (generally found in the primary 

4. Loose connection to binding post (generally found in 
primary circuit). 

5. Wire occasionally grounded through vibration of car. 
This is generally found in the secondary circuit, and it is 
not necessary for the bare wire to make contact with the 


metal into which this secondary current is escaping. If the 
insulation of the secondary cable is weakened, and the cable 
is lying loosely on a metal part, the spark will often jump 
through the insulation. 

6. Timer contact surfaces roughened by sparking. 

7. Wabbling timer. 

8. Poor trembler adjustment. 

9. Trembler sticking at high speeds, due to inertia of 
heavy armature. 

10. Insuflftcient pressure on timer contacts. 

A sticking inlet valve, which stays open when it ought to 
close, will cause irregular firing and occasionally back firing. 
Another possible cause is a very lean or rich mixture ignit- 
ible only by a strong spark. It can always be distinguished 
from ignition troubles by the fact that the explosion 
impulses, when they occur, are of much less than normal 
strength. If the mixture is too weak, the explosions are 
likely to occur every other cycle. 

5. Causes of Weak Explosions. — The causes of the 
explosions being weak are as follows: 

1. Mixture too lean or too rich. 

2. Leakage of compression. 

3. Mixture diluted by exhaust gases. 

4. Spark timing later than it should be, in one or all 

If the trouble is in the mixture, the explosions would be 
regular, unless the mixture is so far defective that it some- 
times fails to ignite in spite of the spark occurring regularly. 
The same will be true in any case where, as is usual, the 
cause of the weakness is unconnected with any irregularity 
in sparking. ' 

The principal causes of weak explosions may be enumer- 
ated as follows : 

1. Dirt or waste in carbureter or gasoline pipe, causing 
weak mixtures. 

2. Stale gasoline. 

3. Air intake partially obstructed, causing rich mixture. 


4. Bad carbureter adjustment. 

5. Trouble with float. 

6. Choked muffler. 

7. Lack of oil on piston, or too thin oil. 

8. Leak through valve (generally the exhaust valve). 

9. Leaky spark plug. 

10. Valve timing wrong. This is most likely due to 
the fact that the cam-shaft, etc., have been taken out and 
replaced with the gears in incorrect angular relation. It 
may, however, be caused also by wear of the cams, push 
rods, or valve stems, by spring in the cam-shaft or valve 
lifters, or by the slipping of cams. 

11. Broken or worn piston rings. 

6. A two-cycle marine engine may be running along 
smoothly and begin gradually to slow down. This condi- 
tion may be caused by too much or too little gasoline; the 
ignition devices may have become disarranged ; there may 
be too little cylinder or other lubrication, or too little water 
circulating through the cylinder jacket; something may be 
caught in the propeller wheel ; in cool or cold weather, the 
moisture in the atmosphere may have become frozen by the 
rapid evaporation of the gasoline, thus preventing the free 
flow of air or the proper seating of the valve in the vapori- 
zer controlling the. gasoline supply and the flow of mixture 
from the crank-chamber ; the piston and rings may have 
been fitted too snugly, causing them to bind in the cylinder, 
which may have become distorted by the different tempera- 
tures to which it is subjected, there being a comparatively 
cold inlet on one side of the cylinder and a hot exhaust port 
on the other; the exhaust ports, piping, or muffler may 
have become partly stopped by water, carbon, salt, or other 
deposits; the exhaust may have been submerged by a differ- 
ent trim of the boat, or there may have arisen conditions 
such as could not have been foreseen or provided against, 
and that might never again be experienced. At any rate, 
such slowing down is a forerunner of trouble and should 
be investigated. If the cause of the trouble cannot be 



discovered, the engine should be stopped when it ii^ safe to 
do so, the position of the boat being made such as not to 
endanger either boat or occupants through collision with 
passing craft. 

7. The remedies for slowing-down troubles due to the 
causes just mentioned will in practice suggest themselves. 
In many cases, the cause of the difficulty can readily be 
determined and overcome. For instance, trouble due to an 
insufficient quantity of cylinder oil or circulating water 
might be attended to readily without stopping the engine, 
or a temporary stop might be made to remove a rope, grass, 
etc. , from the propeller, or foreign matter from the sea-cock 
strainer or pump check- valves, or to adjust the ignition or 
replace a broken or weak valve spring. Structural troubles, 
such as tight pistons and distorted cylinders, would have to 
be attended to at some more opportune time. 

If the vaporizer should freeze, it may be necessary to run 
the engine a while and then give the accumulation of ice and 
frost a chance to melt If the water supply is insufficient 
and the jacket becomes overheated, it may be possible in 
case of an emergency to continue running by using a hand 
pump connected with the supply ; or, with the supply open 
water may be pumped through or poured into the water dis- 
charge. In such case, the transformation of the water into 
steam might make it a little dangerous for the operator, and 
should the cylinder be too hot the water might possibly 
crack the cylinder at its weakest part, or at the point where 
it is subject to the greatest. stress. 

When it becomes necessary to run a four-cycle marine 
engine with too little circulating water, the compression 
should be relieved, the cooling action of the large quantity 
of gas, a part of which is wasted, helping to cool the cylin- 
der, while the smaller amount exploded does not heat the 
cylinder as much as would full charges at the usual high 
compression pressure. 

8, Irregular running of marine engines is a condition 
rarely encountered, and its cause is problematical. The 


trouble may be caused by back pressure in the exhaust, or 
may be due to improper location, with reference to the 
exhaust port, of the transfer, or passover, port connecting 
with the crank-case; this could occur only in two-cycle 
engines. As a result of such improper location of the port, 
the engine cylinder might not be thoroughly scavenged of 
burned gases at high speed, when it would slow down to 
normal speed or slightly below, and, getting a better mix- 
ture at that speed, would speed up. It might also be 
caused by the exhaust ports opening too late or the inlet 
ports opening too early. It is well known that, with no 
thought of fuel economy, two-cycle engine ports should 
open much earlier when designed for high than for low 
speed, in order to more thoroughly get rid of the products 
of combustion. When it is discovered that the engine is 
being run at a speed in excess of that to which it is best 
adapted, the remedy is to make the ports open earlier, or hold 
the engine to slower speed by increasing the diameter, pitch, 
or blade surface of the propeller. 

Should the engine, without missing explosions, begin to 
increase its speed, and then miss explosions and slow down, 
one wbuld naturally be led to suppose the cause of the 
trouble to be insufficient length of contact of the sparking 
device as well as poor scavenging of the cylinder. 

Trouble from loss of compression in the combustion cham- 
ber, whether in a two-cycle or a four-cycle engine, must be 
renledied before the engine can be made to run satisfac- 
torily. If, in attempting to start, it is found that therp is 
no compression, the valves should be examined to see if 
they seat properly and are timed correctly. Loss of com- 
pression may be caused by a leaky gasket, allowing the 
pressure to leak into the water-jacket, which is the first 
place to look for the cause of trouble after examining the 
valves. A leaky gasket may sometimes be discovered by 
noting whether or not pressure escaping into the water- 
jacket shows at the water discharge. 



9, Undoubtedly the sense of hearing is more useful in 
detecting irregularities in the running of an engine than any 
other sense. By means of the sounds produced, the engine 
talks to the operator, and with a little intelligent study he 
will soon understand the language. Even at a distance it is 
often possible to tell whether an engine is running regu- 
larly or whether, as indicated by the sound of the exhaust, 
some of the charges admitted to the cylinder are expelled 
without being exploded. Standing in close proximity to 
the engine, the operator may distinguish a variety of sounds 
indicating defects about the engine and calling attention to 
the necessity of applying proper remedies at the first 

A sharp, knocking soimd in stationary engines may be 
due to any one of the following causes: 

1. Lost motion in the bearings of the connecting-rod, 
either at the crankpin or the piston-pin end. 

2. Lateral movement of a piston ring, the groove in the 
piston having become widened by wear. 

3. A loose key in the flywheel or pulley, 

4. Lost motion in the gears, causing the gear-shaft to be 
retarded in its revolution for a fraction of a second when the 
exhaust or inlet- valve cam hits the roller and lever. 

5. Piston or cylinder worn to a considerable extent, 
causing an up-and-down movement of the piston. 

G. The piston having worn a shoulder in the bore of the 
cylinder, and striking the shoulder if any play in the bear- 
ings is developed. 

7. The piston striking any foreign body that may acci- 
dentally have been drawn into the cylinder. 

10. Knocking in automobile engines may be due to 
looseness or rattle in some external part, owing to nuts hav- 
ing worked loose or to bolts being sheared off or being too 
small for their holes. Knocking due to such causes is readily 
detected by a careful inspection while the engine is runningi 


and this inspection may be aided by l^xnn^^ the l>;^^v1^ tM\ 
parts scspected of bein^ loose, when vibration wUl t\^Mlv 
be felt; also by careful scraiiny with an elcottio tU^hli)iht 
for evidences of movement where t\\x> jvarts aw l>\>lte\l 

Abont the most likely place to tmd hxxsoncNS of thi» 
description is in the holding^-down lH>lts that hold tho onj^ine 
to the frame on which it is mounted; but in vvrtrtin hon^on- 
tal engines it may also be found that the ea^vs owr the nmin 
bearings are loose, owing to the fact that ihey hnvx* not 
been properly tongued into the bi>tlv>ni halXTH or pillow- 
blocks of the bearings. Looseness at cither of thoso l\\*i> 
points should be remedied at the ix^pair slio|\ «» H alwayw 
necessitates the substitution of larger l)«>lls, aiOeil perhaps 
by dowel- pins; and in the case of the ])earing rap it tnay hi» 
necessary to make a wholly new cap, witli prnpor tnn|itu»« 
fitting into grooves that must be luavhiiKMl or rhlmOnl In 
the pillow-block. 

11, A. more probable cause of knocl^inj^ Im Immmimu^mm iIim* 
to wear in the main-shaft bearingH, iTankpIn br/itln^M^ n\ \\\i* 
wristpin bearings. In a four-cylinder veillral ««n^lm*, I In* 
main-shaft bearings may be quite Inn^r wilhont (Mimhiy n 
knock, because the weight of the nhaff and IIvwIm*! IioMm 
the shaft down; but a horizontal cnj/itie will, nnd^'f ifiUilu 
conditions of speed and lo^id, |x>nnrl with a ftfriall afrioimf of 
looseness. Only a very limited amount tff |/»oi•^'r^^•Ji^ Mh^^nld 
be permitted in the main-«^haft l^^iarin;^*; fff nuy ^nJ/lrf^. \tt,fU 
on account of the danger of ^^fT')u*^\u^ fh'- ^\\)i\U /»nd fr' Offi*'>- 
a bearing worn beyond fh:^ ^ixu-ui i«; li/iM/ to t/z-^ln / nttiff^, 
as it is difficult v> kee:> =Jiffj' v-.* oil ;ri it 

12. LoosenetiH :r. *''c ?":/■• K^'/i M;irM.;/ t,f n '//-rfi/Tfl 
motor is di:scIo*^''! V/ y.** -.-^ ;» ;,./ > \r,At r tf,/- n/«/ii//| ,»rid 
working it gently : ^ >r.\ '.v»" T , ♦;./■ ' .^.y /rf ,» K/r7i//fTrMI 

engine it IJ^ r.eCli?*'^'/ V--, ',- ' * ^ .'S.-»f' .;f;f;/r/ifMri»/.i / ^^^ 

line with the or*:<i-if:*', ^•' * '. ^ / , -^z -^/-." rn.o .» i/^ //•!• «/,;i b-f^/^ 
tobeapplied v* * »; ■^■i'*-/ ,- :•..%' ., v*,^»^/«''' r nr»f»M' i* 
seems most pract:iv«'/»* ^y.-.^^^f^.. / ^^/'/-o'v^^ <rf «o'* ^»i'»f' 


can be detected by rocking the fljrwheel back and forth 
against the compression in the cylinder. If the pull of the 
sprocket chain comes on the engine shaft, it may be possible 
to detect looseness in the adjacent bearing by alternately 
stretching and relaxing the chain, which can be done by 
grasping it midway between the sprockets and pulling it up 
and down as far as it will go. 

Another very good way to disclose looseness in the main 
bearings of any car having a planetary transmission gear on 
an extension of the engine shaft is to tighten one of the 
friction bands of this gear by the appropriate lever, usually 
the low-speed or reverse lever. It is very rarely that the 
tension of these bands is exactly balanced, so as to impose 
no radial pull on the shaft, and tightening the band will 
move the shaft to whatever extent the adjacent bearing has 
worn. « 

A novice should not attempt to refit the main-shaft bear- 
ings, as this requires a good deal of skill and experience for 
its correct execution. 

Wear in the crankpin bearings is disclosed by setting the 
cranks at about half stroke, and rocking the shaft back and 

13, Knocking in the wristpin, due to wear of the pin and 
its bushing, is not among the commoner troubles, and it 
does not need to be attended to at once unless aggravated. 
It is well, however, not to neglect it too long, as the bush- 
ings and the pin will be worn out of round, so that they can- 
not be used. A good engine will run a car several thousand 
miles before any replacement is demanded at this point. 
When it is taken out, the wristpin should be calipered 
all around. If it is out of round, it should be ground 
true; or, if this is impracticable, a new pin will have to be 
supplied, and the bushing reamed or scraped to fit. This, 
of course, should be done in a repair shop. 

14, A cause of knocking occasionally found is due to the 
wristpin and the crankpin not being quite parallel. This 
causes the connecting-rod to oscillate from end to end of the 


wristpin and crankpin bearings; and if, as is customary, 
there is -^ or more of end movement in these bearings, the 
knocking may be quite noticeable. If, as is likely to be the 
case, it is impossible to make the pins parallel, the only 
recourse is to take up the lost motion at the end of one or 
the other bearing, and possibly both bearings, by the use of 
washers or cheeks soldered to one end of the bushing and 
brasses. This is not a common cause of knocking, particu- 
larly in the better class of engines. 

16. The best construction is to secure flywheels to short 
shafts by bolting them to flanges instead of keying them. 
Sometimes, however, a flywheel is held on by a common 
key, or by two keys 90® apart, and frequently it will work 
loose on its keys. This will inevitably result in a knock, 
which will be very loud if the engine has less than four 
cylinders. The crank-case should be opened and the cranks 
blocked so that the shaft cannot turn, and then force should 
be applied to the flywheel to disclose the looseness, if any. 
Sometimes the flywheel will be so tight on its shaft as to 
resist turning in this manner by using any ordinary force. 
In this case, it is best to take the car to a repair shop if a 
thorough search has failed to disclose any other cause for 
the noise. 

A sprung shaft will always cause knocking, and also rapid 
wear and cutting of the bearings. 

16. Besides the foregoing mechanical causes of knock- 
ing, there is a class of what may be called combustion knocks 
that are altogether distinct from the preceding, in that they 
may occur without appreciable looseness in the bearings, 
and are due to excessive rapidity of combustion, coupled 
generally with too-early ignition, the charge being com- 
pletely burned before the piston has reached the end of the 
compression stroke. Combustion knocks are due to a vari- 
ety of causes, the most obvious of which is simply too-early 
ignition, as when running up a hill without suitably retard- 
ing the spark. A contributing cause is a slightly weak mix- 
ture, since such a mixture bums faster than a normal or 


overrich mixture. Pounding in particular cylinders of a 
multicylinder engine may be due to unequal rapidity of com- 
bustion, which itself may be due to unequal charges, as 
when the valves are unequally timed, or to irregular spark 
timing, such as may result from a wabbling timer or badly 
adjusted vibrators. If the timer contact surfaces have been 
roughened by sparking or by wear, they will cause the con- 
tact maker of the timer to jump when running fast, and 
therefore to make erratic contact, resulting in irregular 

17. The classes of combustion knocks just mentioned 
are easily traced to their causes. The knocks are not neces- 
sarily violent, and they may sound a good deal like the 
knocks due to loose bearings, except that, if caused by 
faulty action of timer or vibrators, they will occur irregu- 
larly instead of regularly. 

There is, however, another and very common sort of 
knocking due to spontaneous ignition of the charge before 
the spark occurs. This may be caused by overheating of 
the motor from lack of water or other trouble with the cir- 
culation — a trouble at once indicated by boiling of the water 
in the radiator or by smoking of the exterior of the motor. 
It is a temporary phenomenon, and involves no harm to the 
motor if the latter is promptly stopped and allowed to cooL 

18. Much more troublesome, and also more common, is 
spontaneous ignition, or preigrnition, as it is termed, due 
to a deposit of carbon in the combustion chamber or on the 
piston head. A carbon deposit of this nature maybe caused 
by too much gasoline or by too much cylinder oil, and it 
will accumulate gradually even with the carbureter and 
lubrication correctly regulated. A small quantity of carbon 
will give no trouble, but as the deposit thickens some por- 
tions of it will remain incandescent from one explosion to 
the next, and will ignite the fresh charge at some point in 
the compression stroke, depending on conditions. The fact 
that the charge is not ignited until some time during com- 
pression is due to the fact that the more highly it is 


compressed, the more easily it ignites. True preignition 
results almost always, except at the highest engine speeds, in 
the charge being completely burned before expansion begins, 
and it is easily distinguished, especially if the engine is 
taking full charges, by the resulting sound, which is a sharp, 
metallic bing! bing! bing! closely resembling that produced 
by a hammer striking a block of cast iron. Usually, though 
not always, an engine that preignites in this manner will 
continue running by spontaneous ignition for some seconds 
after the igniter switch has been opened. The hammering 
due to preignition, as would be expected, is most marked 
when the engine is running slowly with the spark suitably 
retarded, and it will generally manifest itself when hill 
climbing, owing to the fact that the throttle is then wide 
open and the spark necessarily retarded to suit the slow 
speed of the motor. 

19. In stationary engines, a heavy, pounding noise, such 
as is caused by premature ignition, may also be due to exces- 
sively high compression for the grade of fuel employed. In 
addition to its initial effect in producing a pounding noise, 
either preignition or a too-high compression pressure may 
cause the piston to expand unduly and to stick in the cylin- 
der, which it would not do if the conditions were normal. 
This sticking of the piston would produce a knocking sound 
due to the small amount of play in the connecting-rod bear- 
ings necessary for smooth running. 

A coughing or barking sound is caused by the escape of 
pressure past the piston, and would indicate the necessity 
either of replacing any worn or broken piston rings or of 
reboring the cylinder and fitting a new piston. 

With marine engines, a loose coupling may cause a pound, 
as may also a loose propeller wheel, but these pounds can 
easily be located. 



20. Scored and Ijeaky Cylinders. — One cause of scor- 
ing* of the cylinder lies in the fact that the ends of the piston 
pin or wrist pin when loose sometimes protrude through 
the hole or bearing in the piston. Some pins have their 
bearing in the piston itself, while others, being tightly 
secured in the piston, have their bearing in the upper end of 
the connecting-rod. No matter which construction is 
employed, the ends of the pins should never come in contact 
with the cylinder walls. The pin must by some absolutely 
positive method be kept in place. While a loose wristpin 
is often the cause of a scored cylinder, there are three other 
causes, resulting from imperfections of design or of machine 
work, to which scoring can be traced ; namely, loose core 
sand, imperfectly fitted piston rings, and loosening* of the 
pins that are used to prevent the piston rings from turning in 
the slots in the piston. 

2 1 • Trouble from loose core sand is due to sharp sand that 
usually comes from the cored passage connecting the crank- 
case with the inlet or passover port to the combustion cham- 
ber of two-cycle engines. With cylinder castings prop- 
erly pickled in dilute sulphuric acid to remove the sand, this 
trouble would not be experienced ; but with modem methods 
of cleaning castings by means of the sand blast, the cored 
passages are frequently neglected. Some engines are pro- 
vided with a removable plate over the inlet port, for the 
express purpose of making sure that there shall be no core 
sand therein to cause trouble. 

If, in an engine of the two-cycle type, the scoring consists 
of several parallel marks on the side where the inlet port is 
located, it is safe to ascribe the trouble to sand. If the scor- 
ing is on the exhaust-port side, it is usually an indication of 
insufficient lubrication ; as the hot exhaust gases pass out 
they burn the oil off that side of the piston and cylinder, the 
exhaust side of a two-cycle engine cylinder being always hot- 
ter than the inlet side. Scoring may occasionally be due tu 


the presence in the cylinder of pieces of the porcelain insula- 
tion of spark plugs. Cylinders have been practically ruined 
through dropping into the cylinder the pin or nut holding in 
place the spring on an inverted inlet valve. 

23. Leaky cylinders — particularly in two-cycle engines 
— render the wristpin, crankpin, and main-shaft bearings 
subject to excessive wear, because the heat of the gases that 
pass by the rings into the crank-case tends to bum up the oil 
and heat the bearings. If the engine is of the two-cycle 
type, the leaking products of combustion not only foul the 
fresh charge of gas so Ihat it is not so explosive, but the 
quantity of each charge is reduced. 

If, in an engine in which the inlet and exhaust valves are 
tight and there is no leaky gasket, it is found that the com- 
pression has become materially reduced, the trouble is proba- 
bly caused by leaks from distorted, scored, or imperfect cyl- 
inders, the pistons or piston rings being worn considerably or 
stuck in the slots in the piston. The only remedy is to 
remove the pistons for examination. 

If the cylinder is found to be out of round or scored, it will 
have to be rebored, and new pistons and rings fitted. If the 
rings are found to be rusted or stuck in the slots, they will have 
to be removed, even if to do so it isnecessary to break them. 
They may have worn to such an extent that the openings at 
the points of parting are such as to allow a loss of pressure, 
the leaking charge passing either into the tight crank-case, 
if the engine is two-cycle, or into the atmosphere. If such 
leakage^ is not stopped, the heat of the escaping gases will 
bum the oil out of the crank-case, and the bearings will soon 
become badly worn, if not ruined. 

33. The piston should be examined carefully for wear. 
The side on which the angular pressure of the connecting- 
rod is exerted should, of course, show the most wear. If 
the front or rear side of the piston shows wear at top or 
bottom, with a corresponding amount of wear on the oppo- 
site bottom or top, it is proof that the hole through the 
piston for the piston pin, to which is connected the upper end 


of the connecting-rod, is higher at the end showing wear at 
the top of the piston than at the end showing wear at the 
bottom. If this is found to be the case, and the wristpin is 
tightly secured in the piston, the connecting-rod bearing for 
the wristpin will be found to have worn badly and will be 
bell-mouthed, that is, larger at the ends than at the center. 
The remedy for this is to true up the hole carefully and bush 
it, or use a pin that is a trifle larger than the hole, increasing 
the size of hole in the upper bushing slightly. This is a 
repair job that should be entrusted only to a thoroughly relia- 
ble machinist having the tools and means for doing accu- 
rate work. Side wear on the piston is much more likely to 
show in engines having the wristpin held securely in the 
upper end of the connecting-rod, the ends of the pin having 
bearings in the piston. • 

24# Piston rings become stuck in the slots in the piston 
from two causes ; namely, from water getting into the combus- 
tion chamber, causing the rings to rust, and from the sides 
of the slots being slightly tapered instead of parallel. Where 
tapered sides are found, it is usually necessary to straighten 
them up in a lathe and use slightly wider rings. Piston 
rings should be renewed much oftener than is customan^ 
As they become more and more open at the ends, the hot 
gases passing by the ends of the rings have a harmful effect 
on the polished cylinder surfaces, and in two-cycle engines 
they foul the mixture in the crank-case. 

25. Broken piston rings, particularly in engines with 
ports that are opened and closed by the pistons, are a source 
of annoyance, and frequently cause much trouble. Broken 
piston rings are frequently the result of insuflficient care in 
putting the piston, with the rings in place, into the cylinder, 
but are more likely the result of getting a ring end caught 
in a port. To prevent this, two-cycle engine rings are usually 
pinned to prevent them from turning until the ends can get 
into the port. 

The breaking of a piston ring is rather an unusual occur- 
rence; it will cause loss of compression, that may be 




disdnguished from leakage due to the rings being worn by the 
fact that the broken ring will make a distinct clicking sound 
at the end of every stroke. It will also be found that oil 
squirted on the piston when a ring is broken will not stop the 
Leak. If the engine has more- than one cylinder, it is prob- 
able that loss of compression due to lack of oil would affect 
all the cylinders, whereas a broken ring affects one only. 
If a piston ring is broken, it becomes necessary to take off 
the cylinder without delay and put in a new ring. 

26. Piston rings are supposed to be held in position by 
small pins, one in each 
ring, so that the joints of 
adjacent rings are diamet- 
rically opposite. If for any 
reason these pins break, a 
ring may slip roimd until 
its joint is in line with 
that of the next ring above 
or below. This will cause 
loss of compression that 
may be very puzzling; it 
is an unusual occurrence, 
and it may be necessary to 
take off the cylinder to 
locate the trouble. 

37. A good method 
for pinning piston rings is 
shown in Fig. 1 {a) and (^). 
Fig. 1 {a) is a diagram of 
a piston head, the dotted 
lines showing the bottom 
of the ring slot, while Fig. 
1 (d) is a sketch of a por- 
tion of one side of the 
piston. With the piston square on its lower end, drill, at a, 
a point about half way between the inlet and exhaust ports, 
through dy r, and d, a hole large enough for clearance for a 


small tapy continue the hole into e with a tap drill, tap the 
hole, and screw into it a slotted screw to extend into the slot 
for a distance not quite one-half the width of the slot. Then 
tap and plug the hole through ^, r, and rf with screws dipped 
in muriatic acid to rust them in place, the screw plugs being 
in each case below the surface of the slot faces. At another 
point, where it would not come opposite a port, drill a hole 
through b and c and tap into //, plugging the clearance holes, 
as before. Drill at another point a hole through ^, tapping 
into c. The slotted screws extend one-half or less the width 
of the slots from the bottom, so that, if the rings be 
parted as in Fig. 2 {a) one of the ends could be cut off 
slightly to receive the pin, or, if parted diagonally, as in 

, Fig. 2 {b\ a space could be cut out 

1 for the pin. With this method of 


^^) pinning the rings, there is no way for 

the pins to work out to score the cyl- 
inders. While it is customary to pin 
the piston rings for two-cycle engines, 
(^^ pins are rarely found necessary in 

^'°* ' four-cycle engines, as such engines 

have no ports to catch the ends of the rings, except when an 
auxiliary exhaust is employed. 

2 8 . Cyllndep-Packlnfif Troubles. — The joints between 
the cylinder head and the cylinder of stationary gas engines 
are kept tight by packings usually cut out of asbestos 
sheet about -^ inch thick. When the packing is dam- 
aged by overheating or excessive pressure, water from the 
jacket leaks either to the outside or into the cylinder. The 
latter is the more serious leak of the two, as it interferes 
with the running of the engine by corroding the points of 
contact on the igniter and the valve seats and stems, and 
prevents proper lubrication of the piston and cylinder. Leak- 
ing toward the cylinder is generally indicated by splashing 
of the cooling water at the overflow pipe when the explosion 
tfl.kcs place. 

In most cases, the blowing out of a packing is caused by 


the combustion pressure opening the joint between the 
packing surfaces, the packing being heated and partly 
destroyed, and allowing water to enter the combustion 
chamber. A partial or complete stoppage of the cooling- 
water supply or the clogging of the water spaces with lime 
or similar deposits will also result in the overheating of the 
cylinder and consequent damage to the packings. 

As soon as a leak of water from a faulty packing develops, 
preparations should be made to renew the packing at the 
first opportunity. If the leak is to the outside, which may 
not interfere with the operation of the engine, although it 
will cause inconvenience through having to catch the water 
in buckets, it is not necessary to shut down the engine until 
the day's work is done. If the leak is toward the combus- 
tioil chamber, the engine will generally stop in a short time. 

29. Most automobile engines have the cylinder heads 
and cylinders in one piece; but a few engines have copper 
or aluminum water-jackets. There are, however, some old 
engines with separate heads still in service. In some cases, 
the cylinder heads, when separate, are made a ground fit on 
the cylinders, but they are commonly made tight by asbes- 
tos gaskets. Leakage through these may be detected some- 
times by the soimd, and sometimes by putting a little oil 
over the suspected place and noting the resulting bubbles 
when the crank is turned. 

In case a cylinder-head gasket leaks, it will be necessary 
to put in a new gasket. The head should be taken off, 
the old gasket removed, and the iron surfaces in contact 
with it should be carefully scraped clean. The new gasket 
may be of sheet asbestos, and it should be sprinkled evenly 
with powdered graphite to prevent it from sticking. It 
may be cut to size by laying it on the cylinder and tapping 
it lightly with a small hammer to indicate the outlines. 
Care should be taken not to let inwardly projecting edges 
interfere with the valves or igniters; and, also, if there are 
openings througfh the head for the passage of water, it 
should be seen to that these are not closed, by the asbestos. 


A good packing for cylinder heads is sheet asbestos with 
woven brass wire embedded in it. This packing is much 
^^tronger than ordinary sheet asbest6s, and will not blow out 
•jnless the cylinder-head bolts are loose or the head is a bad 
lit In replacing a cylinder head, the bolts should be tight- 
ened gi^adually and evenly, each being tightened a little at a 
time, and the round being made three or four times, so as 
to ^void localizing the stress on any one bolt. 

There is, of course, but one remedy for leaky gaskets, 
namely, renewal. The old gasket should be carefully and 
completely removed, and by means of a straightedge a care- 
ful examination should be made to discover, if possible, why 
the gasket gave way at a particular point. There may have 
been insufficient surface or too little holding-down pressure 
to keep the packing in place ; the studs may have been too 
fa. apart at the point of rupture, or the nuts may not have 
been tightened after the engine had become heated. 


30. Lieaky Inlet and Exhaust Valves. — Trouble from 
loss of compression in the combustion chamber, when the 
spark plug is tight and there is plenty of oil on the piston, 
is generally due to leaky valves. In order to determine 
whether the leak is in the valves or in the piston rings, a 
moderate quantity of oil may be squirted through the com- 
pression relief cocks and the crank turned two or three 
times, which will temporarily check whatever leakage there 
may be around the piston. If the compressed charge still 
escapes, the inlet valve, if located over the exhaust valve, 
may be taken out and examined. The leak, however, is 
much more likely to be in the exhaust valve. 

To take out the exhaust valve, turn the engine over by 
hand, with the switch off and the compression relief cocks 
open, until the valve is opened. Then prop up the valve 
spring with two pieces of wood or brass ^, «, Fig. 3, cut to 
the proper length to go between the spring collar by and the 
upper end (or lower end, if this is more convenient) of the 




Pig. 8 

push-rod guide c, and turn the engine again until the push 
rod d is down as far as it will go. Push the exhaust valve 
down; the key at e may now be slipped out. If the props 
have been made accurately to length, the 
valve may be slipped up and out, leaving the 
spring and the collar in place. Inspection 
should show the valve seat to be of uniform 
appearance all the way around,, and dull — not 
glossy. If the seat of either valve is pitted 
or rough, or if it is worn bright on one side, 
showing that it has been seating only on that 
side, it should be reground. 

31. The remedy for leaky valves is to 
reg^nd them to their seats. If badly scored 
and worn, which will be shown by a blacken- 
ing of the seat and valve, it may become nec- 
essary to reseat and true up the valve, but if 
the engine has had ordinary care and attention, grinding 
should be sufl5cient For this purpose, the exhaust valves 
may need emery and oil, finishing up with powdered oilstone, 
ground glass, silex, or the dirt that accumulates under a 
grindstone. The valve should not be rotated its whole cir- 
cumference — as is frequently done, using a brace or breast 
drill with a bit screwdriver — but should be rotated a little, 
first in one direction and then in the opposite direction, rais- 
ing it off the seat very often, and using oil freely, until a dull 
surface appears on both the valve and the seat throughout 
their bearing surfaces. Rotating the valve rapidly is very 
likely to cause grooves and ridges that are extremely hard to 
remove and make the valves tight. 

While there is little or no danger of getting emery or 
other abrasive substance into the cylinder when grinding 
exhaust valves, ordinary care to avoid doing so should be 
exercised. The passage of the products of combustion 
being outwards, such matter would be carried away from 
the cylinder. Grinding the inlet valves is a very particular 
operation, for any particles of abrasive substance left behind 



to be drawn into the cylinder are liable to cause trouble. 
All traces of grindstone dirt, which will be found well 
adapted for grinding and may be mixed with water instead 
of oil, should be wiped off carefully. 

The valve stems should be inspected, and, if rusted or 
rough, should be cleaned and smoothed, a few drops of 
kerosene being applied to cut any deposits that may have 
accumulated in the guides. 

33. Weak or Broken Inlet-Valve Sprinsr* — Some- 
times the inlet- valve spring, especially if the valve is of the 
automatic variety, will weaken from becoming overheated 
This is almost sure to occur if the engine has been allowed 
to overheat from lack of water. In time a spring loaded 
too near its elastic limit will break from the jarring to which 
it is subjected. The symptoms in either case are loss of 
power at high speeds — although the power may still he 
ample at low speeds — and clattering of the valve and blow- 
ing back in the intake pi{)e at high speeds. The latter 
may easily be detected with a single- or double-cylinder 
engine by holding the fingers close to the air intake, when 
the backwards puffing will be very perceptible. If the 
engine has four cylinders, it may be possible for the inlet- 
valve springs to be slightly weak without the mixture blow- 
ing back at the intake, owing to the fact that one or another 
cylinder is aspirating all the time, and the air expelled from 
one cylinder is drawn into the next. One way to get 
around this difficulty is to block open the exhaust valves of 
two cylinders — the first and fourth or the second and third- 
while the others are tested. It will probably be simpler, 
however, to experiment with the valve-spring tension. If 
the valve spring is weak, and if it is temporarily increased 
in stiflEncss by putting washers under it to compress it, a 
marked increase in the power of the motor at high speeds 
will be observed. The proper remedy, however, is to put 
in a new spring, or, if this cannot be done, to stretch the 
old spring. For a valve lift of ^ inch, and for average 
engine speeds, the tension should not be less than 1 pound 


per ounce of the weight of the valve, washer, and key. The 
engine will work better if the springs arc a little too stiff 
than if they are not stiff enough. There will also be less 
danger of breakage of the valve stems and keys. 

33. Unequal Tension of Automatic Inlet-Valve 
Sprtn^s. — The effect of unequal tension in the springs of 
automatic inlet valves is to permit one cylinder to take more 
gas than another. Consequently, at slow speeds the cylin- 
der whose valve spring is weak will get the larger charge; 
and at high speeds part of the charge will be blown back 
through the valve whose spring is weak, so that the other 
Cylinders will get stronger impulses. A quick way to test 
the equality of valve-spring tension without taking out the 
valves is to run the engine slowly with the throttle almost 
closed. This will cause the cylinders whose springs are 
stiffer to receive scarcely any gas, and the cylinders whose 
valve springs are weak will do most of the work. It is 
possible, however, to go to excess in a test of this sort, 
since, when a motor is running light with the minimum 
quantity of gas, one cylinder is almost sure to get more gas 
than another, if the inlet valves are automatic, even with 
the most careful equalizing of the springs. If the tension 
of the valve springs is under suspicion, the valves should be 
taken out and the springs tested by compressing the valve 
stems together. 

34. Excessive Liift of Automatic Inlet Valve. — The 

lift of an automatic inlet valve should be proportionate to 
the spring tension and to the weight of the valve, so that 
the spring will be able to overcome the inertia of the valve, 
and close it before the piston has started so far on its com- 
pression stroke as to expel any of the mixture through the 
open valve. 

The symptoms of too great a valve lift are loss of power 
and blowing back at high speeds. A valve 2 inches in outer 
diameter should not ordinarily lift more than \ inch and a 
lift of -^ inch would be excessive for almost any valves 
found on high-speed engines. An excessive lift, like a weak 


spring, is likely to result in breakage of the valve stems and 
keys through unnecessary hammering of the valve when 
opening and closing. 

35. Broken Inlet-Valve Stem or Key. — Trouble from 
a broken inlet- valve stem or key is more likely to occur with 
automatic valves than with those mechanically operated. 
The result, if the valve opens downwards, is to let it stay 
open all the time, causing that cylinder to cease work, while 
the sparks from the plug ignite the mixture in the intake 
pipe and cause explosions there and in the carbureter. If the 
valve, whether automatic or mechanically operated, opens 
upwards, it will clatter on its seat and -permit much of the 
mixture to be expelled during the first part of the compres- 
sion stroke. 

36. Weak op Broken Exhaust- Valve Sprinsr* — Owing 
to the heat to which it is subjected, the exhaust- valve spring 
is more likely to weaken than that of the inlet valve. The 
symptoms are loss of power, owing to the valve lingering 
open at the end of the exhaust stroke, and clattering when 
the valve closes. 

37. Broken Exhaust- Valve Stem or Key. — As there 
is nothing to prevent the valve from being sucked wide open 
on the suction stroke, an accident of this kind will generally 
cause that cylinder to go out of action entirely. The clat- 
tering, if the engine continues running by virtue of other 
cylinders, is likely to be marked. 

38. Slipped Valve Cams. — Some cheaply constructed 
motors have the valve cams held on the shaft by taper pins 
that in time shear partly or wholly through, permitting the 
cams to turn on the shaft. The cams may turn a short dis- 
tance and then be jammed by fragments of the taper pins. 
The symptom indicating trouble due to this cause is partial 
or complete loss of power in the cylinder affected, when noth- 
ing is wrong with the ignition, valve-spring tension, etc.; 
and it will be equally marked at all speeds. If a cam is pinnec 


on its shaft, the proper way to secure it is to add another 
pin, or, better, to add a key to take the torsional stress, 
and depend on the pin only to keep the cam from slipping 
endwise on the shaft. 


39. liack of Cylinder Oil.— The symptoms of lack of 
cylinder oil are manifested in a sudden laboring of the engine, 
a dry or groaning sound, and partial loss of compression, fol- 
lowed by probable seizing of the piston. If the piston does 
not seize, it and the cylinder walls will at all events be 

Among the causes of lack of cylinder oil are clogging of 
lubricator by dirt or waste, obstruction in oil pipes, leaky 
check-valves, leaky pump packing, broken oil pipe, oil too 
cold to feed, lack of oil in crank-case, etc. 

The remedies for trouble from 'this source will become 
obvious on inspection. The motor should be stopped and 
allowed to cool, and a liberal quantity of oil should be put in 
the crank-case before starting again. Squirt a little oil 
through the compression relief cocks to insure lubrication of 
the pistons, without waiting for oil to reach them from the 
regular sources. Remove the obstruction or repair the 
break as soon as possible. 

40. liBck of Oil In Bearlngfs. — A slightly loose main 
or crankpin bearing will sometimes be cut badly as a result 
of a temporary stoppage of oil feed, and yet give no notice- 
able symptom until the bearing is so badly cut that knock- 
ing begins. If a well-fitted bronze-bushed bearing becomes 
dry, it is more likely to stop or at least retard the engine. A 
babbitted bearing will melt out and let the shaft settle 
as far as other supports or bearings will allow. The result 
may be a violent pounding, a bent or broken shaft, or cut 
bearings generally, according to the particular conditions. 
There is no real safeguard against lack of oil in bearings 
except in the vigilance of the operator, combined with a sys- 
tem of oiling not liable to go wrong. It is not safe to depend 


on detecting a dry bearing by the sense of touch, because 
often the metal adjacent to bearings is sufl&cient to carry the 
heat away. 

Generally, trouble from this cause is due to neglect to 
supply oil or to see that the sight feeds are working properly. 
It may also be due to a broken pipe, cold oil, etc. 

There is no excuse for neglect to clean the oil strainer, 
or failure to inspect the oil pipes, unions, etc., or to know when 
starting out how much oil is in the crank-case. A badly cut 
bearing should be sent to a repair shop, and should be 
attended to without delay; but a bearing only slightly cut 
may be kept in service by t^ie addition of a small quantity of 
flake graphite to the oil. If possible, the shaft should be 
taken out and polished with emery cloth and oil, else 
bronze from the bearing is likely to cling to it and aggravate 
the cutting. A bearing supplied with oil from a well 
beneath it, and a chain running over the shaft, may occasion- 
ally fail to receive oil owing to the chain catching on some 
internal roughness or projection in the oil pocket It is 
always safest to keep a more or less regular supply of oil pass- 
ing through bearings of this sort when in use, and depend on 
the oil well only as an equalizer. 

41, Improper Oil In Cylinders. — The trouble symp- 
toms produced by the use of oil unsuited for lubricating the 
piston are white or yellow smoke in the exhaust, rapid foul- 
ing of spark plugs, partial clogging of inlet and exhaust 
valves, and rapid accumulation of carbon on the valves in 
the combustion chamber and about the piston rings. 

To remedy the trouble empty out all the unsuitable oil if 
possible, and substitute oil known to be good. Inject kero- 
sene freely through the compression relief cocks to loosen the 
carbon deposit on the piston rings, and use kerosene to 
free the valves if they stick. Drain the crank-case, and, 
if possible, open it and clean out any carbon that may have 
worked down past the piston and mingled with the oil. Change 
all the spark plugs, and clean them when opportunity offers. 
Put in plenty of fresh oil before starting, and see that oil is 


supplied to the pistons so that they will not go dry before 
oil begins to feed from the cylinder lubricator. 

43. Too Much* Oil on Pistons. — Too much oil on the 
pistons is indicated by white smoke in the exhaust, fouled 
spark plugs and valves, substantially as when inferior oil is 
used, though the symptoms will not be so pronounced. An 
examination of the combustion chamber through the inlet 
valve or spark-plug hole, using a mirror and electric flash- 
light if necessary, will show an unnecessary amount of oil 
around the top of the piston. With the oil Correctly regu- 
lated, it should not accumulate on the piston head in any 
great quantity. 

Trouble from this source is remedied by drawing off part 
or all the oil from the crank-case, if it contains more than is 
necessary for running the engine, and reducing the oil feeds 
to the cylinders if necessary. 


43, Ijack of Water. — Lack of water in the radiator of 
the cooling system for automobile engines is indicated by 
the rapid emission of steam, if there is sufficient water to 
entef the engine jacket; the bottom of radiator being cold; 
the overheating and smoking of the engine, follo\ved by 
laboring, groaning sounds, owing to the oil being burned 
away faster than it is supplied to the pistons; and, if the 
engine still continues running, expansion and seizure of the 
pistons in the cylinders. 

Trouble from lack of water is due to carelessness in not 
filling the tank before starting; leakage in radiator or 
piping; accidental opening of the drain cock at the lowest 
point of the circulation system; breakage of drain cock by 
flying stone, etc. 

The remedies for such trouble are apparent on inspection. 
If the motor becomes overheated so that the water boils 
rapidly away, and there is reason to think that the upper 
portion of the water-jacket is dry, the motor should be 


allowed to cool before water is added; otherwise, the sud- 
den contraction may warp or even crack the cylinders^ or it 
may cause the cylinders to contract and seize the pistons. 
If the water gives out when at some distance from the near- 
est source of supply, the motor may be allowed to cool off 
and the car then run with throttle nearly closed, and the 
spark advanced as much as it will bear without knocking. 
This may be kept up sometimes for ^ mile before it is neces. 
sary to stop to cool the motor. The crank-case should be 
liberally supplied with oil to prevent the pistons from becom- 
ing dry, or, if a sight-feed oil cup is put on the cylinder, it 
should be set to feed quite rapidly. The motor should be 
stopped at the first sign of distress, as indicated by a groan- 
ing sound, turning with difficidty, or knocking caused by 
preignition due to hot cylinders. 

44, Obstructed Circulation. — ^An obstruction to the 
circulation of the cooling water elsewhere than in the radia- 
tor will cause the bottom of the radiator to remain cool 
while the top is, probably, boiling hot. 

Among the causes of obstructed circulation are a broken 
pump, broken driving connection to pump, or slipping belt 
or friction pulley, if the pump is driven in that manner; 
waste or the like lodged in the pump or piping. 

The remedies for this trouble will become obvious on 
inspection. If the belt or friction pulley has oil on it, gaso- 
line may be used to clean the pulley, as well as the fly- 
wheel if it drives the pulley. 

45. St^le or Sediment In Radiator. — ^The presence of 
scale or sediment in the radiator is indicated when the whole 
radiator becomes hot or when steam formed in the jacket 
forces water out of the upper pipe to the radiator, there 
bein^v^ no oil on the inside or dirt on the outside of the 

Scale will deposit from hard water if the temperature of 
tlio water is allowed to approach the boiling point. A simi- 
lai scale. alni.>st iirpussiMc lo eliminate, will crv'stallize 


from caldum-chloride non-freezing mixtures if these are 
allowed to become supersaturated. 

A radiator badly choked with lime scale is practically 
hopeless, although, if it is made entirely of brass and cop- 
per, it may sometimes be helped by the use of a dilute solu- 
tion of hydrochloric acid in the proportion of about one of 
acid to ten of water. This should be left in the radiator 
long enough only to loosen the scale, and should then be 
drawn off, and the radiator washed out. It is better in 
doing this to disconnect the radiator from the engine, in 
order to confine the effects of the acid. Another method is 
to use washing soda, as explained in Automobile and Marine 
Engine Auxiliaries, Ordinary dirt may be cleaned out by a 
strong, hot solution of lye, which should be used with care, 
as it bums the skin badly. Rainwater should be used wher- 
ever possible, and all the water should be strained. 

46. Dirty Radiator. — When the whole radiator is hot 
and it is impossible to run in low gear without boiling the 
water, the circulation being good, it is evident that the 
radiator is dirty. 

Flying oil about the motor may lodge on the air surfaces 
of the radiator tubes, and gather dust, which forms a non- 
conducting covering. Oil sometimes gathers on the water 
surfaces by gradual escape from the pump bearings, or may 
remain after an attempt to substitute refrigerator oil for 
water as a cooling medium in freezing weather. The film 
of oil, preventing the water from coming in contact with the 
metal, acts practically as an insulator. 

To remove the oil from the radiator use kerosene, or a 
mixture of kerosene and mineral-oil soap. Dissolve the 
soap in water and add it to the kerosene, fill up the radiator 
with the mixture, and run the car for an hour or more until 
the radiator gets well heated. The soap and kerosene will 
form an emulsion with the oil, and when the mixture is hot 
it may be drawn off and the radiator washed out with cold 
water. For the removal of the external oil and dirt, use 
gasoline, with a brush or swab. 


A simple trouble, but one likely to be mistaken by the 
novice for radiator or circulation trouble, is slipping of the 
fan belt. The belt should be tested occasionally, and not 
allowed to g^et so loose that the fan pulley can spin inside it 
It does not need to be tight. 



47, Ovenich Mixture. — If a mixture is very rich, that 
is, if there is an excessive amount of gasoline in the charge, 
the fact will be manifested by black smoke in the exhaust. 
If the mixture is not rich enough to produce smoke, it will 
still produce an acrid odor in the exhaust, and will cause 
overheating of the radiator, unnecessary sooting of the 
plugs, accumulation of carbon in the combustion chamber, 
and unnecessarily rapid comsumption of gasoline, with 
diminished power. An automobile of from 12 to 20 horse- 
power, running at an average speed of 20 miles an hour, on 
good and fairly level roads, should be able to cover 20 miles 
on a consumption of a United States gallon of gasoline. If 
it does not do this, the carbureter is incorrectly adjusted or 
is inefficient. 

The causes of an overrich mixture are: faulty carbureter 
adjustment; leaky float; leaky float valves; float too high 
on its stem or too heavy; spray nozzle loosened or unscrewed 
by vibration; and dirt on the wire-gauze screen over the 
mouth of the air-intake pipe. 

For float troubles, see Arts. 53 to 55, inclusive. Dirt 
over the intake may have gathered gradually or it may have 
been splashed on from a muddy road. Its effect is to 
increase the suction in the spray chamber and to diminish 
the air taken in. If necessary, a shield should be fitted to 
prevent mud from reaching the air intake and carbureter. 
If the float is in good order, the carbureter will probably 
need readjustment. 



48. Flooding: is the most common source of trouble in 
marine engines using vaporizers. It is caused by leakage 
of gasoline into the vaporizer, from which in a two-cycle 
engine it readily runs into the crank-chamber; the resulting 
mixture is too rich in gasoline, and, not having sufficient 
oxygen, is unexplosive. When trouble from flooding is sus- 
pected, turn the engine over two or three times, with the 
gasoline valve and the switch closed. If there is an explo- 
sion, note the color of the flame at the relief cock, or priming 
cup, which should be left open for the purpose. If no explo- 
sion occurs, leave the cock or cup open and slowly turn the fly- 
wheel to a point just before the exhaust port opens, thus draw- 
ing air into the cylinder through the priming cup to dilute 
what is thought to be an overrich mixture. Now revolve the 
flywheel in the opposite direction rather rapidly until the 
spark occurs. If there is no explosion, try again, and 
repeat the operation two or three times if necessary. If an 
explosion then takes place, it is evident that flooding is 

To remedy this in a two-cycle engine, open the draw-off, 
or drain cock in the lowest part of the crank-case, and draw 
off the contents, taking care, however, to replace with a 
fresh supply the lubricating oil thus drawn out. If there is 
no draw-off cock, it will be necessary to turn the flywheel 
many times to exhaust the excess of gasoline in the crank- 
case, leaving the switch closed and the compression relieved 
as much as possible. After a while, an explosion should 
take place, then another, gradually becoming more frequent, 
until finally the engine may run with an explosion at every 
other revolution or so. The gasoline valve should be kept 
closed until the charges explode regularly and the red 
tinge to the flame at the relief cock and smoky exhaust dis- 
appear, after which the gasoline may be turned on and regu- 
lated at the needle valve in the vaporizer, closing it 
slightly at first; and, if the engine slows down somewhat, 
open it slightly until it is possible to tell whether it is get- 
ting too little or too much gasoline. 

In case of flooding in a four-cycle engine using a vapori- 


zer, two or three revolutions of the crank-shaft will usually 
dispose of any excess of gasoline, for there cannot be as 
large an amount in the exhaust piping of a four-cycle engine 
as could accumulate in the crank-case of a two-cycle engine. 
Trouble from flooding in a two-cycle engine is the first 
thing to be suspected when an engine of that type refuses to 
start readily. 

If the cause of a failure to start is found to be an insuf- 
ficient supply of gasoline, due to dirt in the needle valve, or 
to a small amount of water in the gasoline piping, lift the 
valve in the vaporizer from its seat and let a little gasoline 
run through to clear the obstruction or get a drop or two 
of the water out, being sure to catch the drip for exami- 
nation. If there is any water it will show in globular form 
at the bottom of the vessel. In case water is found, the 
pipe must be disconnected and drained, and any water in 
the tank must, if possible, be removed, for a single drop of 
water will completely close the aperture in the seat of a 
needle valve. 

49. Weak Mixture. — Among the symptoms produced 
by a weak mixture are insufficient power, although the 
explosions are regular; a tendency to preignite or to bum 
very rapidly if there is the slightest carbon deposit; the 
engine sometimes will miss every other explosion. There 
is likely also to be difficulty in starting the engine. It is 
not always easy to distinguish between lack of power due to 
an overrich mixture and that due to a weak mixture, but 
the tendency of the former is to produce black smoke and of 
the latter to preignite and miss explosions. Some experi- 
menting with the carbureter adjustment will often be neces- 
s«'iry to settle the point. 

Nearly all the causes named in Art. 47 will make a mix- 
ture richer at some speeds than at others, and if the carbu- 
reter has been readjusted, for example, in the attempt to 
correct trouble due in reality to a heavy float, the result will 
be to make the mixture faulty again at certain other speeds. 
Special causes of weak mixture are dirt or waste in the 


gasoline pipe or strainer; stale gasoline; carbureter too cold 
to vaporize ; dirt in the spray nozzle ; float too light or too 
low on its stem. 

For float-trouble remedies see Arts. 53 to 55, inclusive. 
Experimenting with the carbureter adjustment should be 
very cautiously done, with the original setting or adjust- 
ment marked so that it can be restored if necessary. The 
carbureter should then be adjusted slightly in one direction 
or the other, and the effect noted before further change is 
made. Very often a combination of adjustments will be 
necessary, but it is best to make them one at a time. If a 
radical change is made, it may be very difficult to start the 
motor at all, and this would leave the experimenter com- 
pletely in the dark as to what was required. 


50. Dirt In Carbureter. — If there is dirt in the float 
valve, it will prevent the latter from closing and will cause the 
carbureter to flood. This will produce an overrich mixture, 
especially at low speeds, and is highly dangerous on account 
of the liability to fire. If the dirt is in the spray nozzle, it 
will produce a weak mixture. If the dirt has been splashed 
into the air intake, it will produce an overrich mixture, 
especially at high speeds. 

The remedies for trouble due to dirt in the carbureter 
will become obvious when the nature of the trouble is located. 
A carbureter that has previously worked well and that sud- 
denly begins to leak has in all probability dirt in the float 
valve. A carbureter that suddenly gives a very weak mix- 
ture has dirt probably in the gasoline pipe, strainer, or spray 

51. Dirt or Waste In Gasoline Pipe. — It is a common 
practice to carry a bunch of waste under the seat of an auto- 
mobile. Usually, the gasoline tank is near the seat, and in 
time a sufficient quantity of fluff from the waste may enter 
through the vent-hole in the feed- cap of the tank to create 


an appreciable obstruction in the gasoline pipe. Even if 
this does not happen, dirt or other obstructions sometimes 
accumulate, especially if the gasoline has not been properly 
strained. The symptom is a sudden or gradual weakness of 
the mixture, necessitating readjustment of the carbureter in 
order to keep the engine running. The most probable 
place of lodgment for obstructions of this sort is in the gaso- 
line pipe where the latter connects to the carbureter, or at 
the strainer, through which the gasoline generally passes just 
before it enters the float chamber. Disconnecting the gaso- 
line pipe or the union exposing this strainer will generally 
disclose the obstruction. Sometimes it may be necessary to 
disconnect the gasoline pipe at both ends, and blow it out 
with the tire pump. This is necessary only when the pipe 
has been disconnected near the carbureter and" gasoline does 
not flow freely from it when turned on at the tank. 


53, licaky Float Valve. — With a leaky float, the car- 
bureter drips when the main gasoline valve is opened. The 
leakage is not stopjDed when the top of the float chamber is 
opened and the needle valve pressed down with the finger, 
or when the mixing chamber is opened and the spray nozzle 
covered with the finger. 

To remedy the trouble grind in the valve with pumice or 
fine sandstone. 

53, Float Too nigrh. — By the expression yfo^/ too high 
is meant that the float is set too high on its stem so that it is 
not lifted by the gasoline sufficiently to close the float valve 
before gasoline escapes from the spray nozzle. 

When this trouble is present, the carbureterdrips when the 
main gasoline valve is opened; but the float valve is soon 
closed by the float if the spray orifice is covered by the finger. 
The float valve closes tight when manipulated by the fingers, 
or wlien the float is lifted by a pair of bent wires. When 
the trouble is due to a hii>h float, it will be foimd that the 


float itself is empty, and, if of cork, that it is not gasoline- 

Unless the float is adjustable on its stem, the easiest reme- 
dy for this trouble is to bend the levers by which the float 
acts on the float valve. If this cannot be done, shift the 
float ^ inch lower on the stem by the use of a soldering 

54. Float Too Heavy. — The same symptoms are pres- 
ent when the float is too heavy as when the float is too high, 
but they are caused generally by a leak in the float or by its 
being gasoline-soaked. 

If the float is hollow, it will sometimes be found that there 
is present in it a minute leak due generally to some oversight 
in soldering. If the float is taken out and shaken with 
the hand, the presence of the gasoline inside of it will at 
once be apparent. The float should be immersed in warm 
water until all the gasoline in it is slowly boiled away and its 
vapor has been expelled through the aperture in the float. 
By holding the float under water, the escape of bubbles will 
indicate this aperture. Care should be taken that the vapor 
escaping from the float does not cause fire. When the leak 
has been located it should be marked with a pencil, and after 
the float has become cold the leak may be closed with a 
minute drop of solder. If the float is of cork, it may be satu- 
rated with gasoline. It should be taken out, allowed to 
dry slowly, and given a coat of shellac, care being taken that 
the shellac enters all the holes on the surface. 

55. Float Too lAglit or Adjusted Too IjO-w. — By the 

expressions ^oat too light or adjusted too low is meant that 
the float is lifted by the gasoline in the float chamber when 
the gasoline level is still some distance below the orifice of 
the spray nozzle. 

Among the symptoms produced by a light float or a low 
adjustment are a weak mixture at slow speed, and, probably, 
difficulty in starting the engine, owing to the fact that con- 
siderable suction is required to lift the gasoline to the mouth of 
the spray nozzle. The height of the gasoline in the spray 


nozzle can generally be determined, with the aid of an electric 
flashlight, by a little experimenting with the float, pushing 
the latter down for an instant after it has closed the valve. 

To remedy the trouble, the float must be weighted slightly, 
so that t6e gasoline will rise higher before the float closes its 
valve. The weight may take the form of a few drops of 
solder carefully distributed over the float so as not to over- 
balance it on one side; or, if this is not sufficient, a ring 
of sheet brass may be soldered to the top of the float. 


56. Stale Gasoline. — If an automobile has been left 
standing for some time unused, more or less of the gasoline 
in the tank will evaporate, and it may get too stale to give a 
correct mixture without readjustment of the carbureter. 
The usual symptoms are difficulty in starting the engine, 
and insufficient power owing to a weak mixture. The best 
remedy is simply to fill up the tank, when the mixture of 
old and fresh liquid will probably work satisfactorily. It 
may be necessary, however, to readjust the carbureter or to 
throw away the stale fuel. It frequently happens when 
touring that the gasoline procured at country stores is very 
stale, and it is safest to test it with a hydrometer before 
accepting it. The user should know for what density his 
carbureter is adjusted, and should not depart from this 
more than is necessary. Ordinary stove gasoline is sup- 
posed to test 74° or 76° Baum6, but is frequently found 
testing as low as 68° or 66°. 

57, Water In Gasoline. — Water may be found in gaso- 
line taken from a barrel standing out of doors. The water, 
being heavier than the gasoline, will always settle to the 
bottom, and by close observation it may be seen before it is 
poured into the tank. If the gasoline is strained through a 
piece of chamois skin or several layers of cheese cloth, or 
even through very fine brass-wire gauze, the strainer will hold 
the water while permitting the gasoline to pass through. 


The user should make it an invariable rule to strain his g-aso- 
line in this manner. 

The symptom of water in the gasoline will be immediate 
stoppage of the engine when the water reaches the spray 
nozzle, in spite of the fact that the timer, coils, battery, 
spark plugs, etc. , are in perfect order, and the gasoline tank 
is known not to be empty. The only remedy is to unscrew 
the wash-out plug at the bottom of the carbureter, and let 
the water and gasoline run out until it is certain that all the 
water has escaped. Sometimes it may be necessary to dis- 
connect the gasoline pipe entirely and blow it out in order 
to expel the last drop of water. It is well also to look into 
the tank with an electric flashlight and see if any drops of 
water can be discovered on the bottom. If so, it may be 
well to drain the entire tank. Extreme care should be taken 
to avoid fire while gasoline is being run off. 

58. In stationary practice, besides using gasoline of 
proper quality, it is of course supposed that the storage tank 
contains a sufficient quantity of fuel to run the engine. This 
appears to be a superfluous precaution, nevertheless it has 
frequently happened that an expert has been sent several 
hundred miles, on complaint from the purchaser of an 
engine that he was unable to start it, only to find that there 
was no gasoline in the tank. In other cases it was discov- 
ered that, instead of gasoline, almost pure water was 
pumped to the engine. The explanation was that fuel pur- 
chased from a local dealer contained a considerable quantity 
of water, which of course settled to the bottom of the tank, 
and accumulated gradually until with the tank about one- 
quarter filled, nothing but water would be delivered to the 
engine. To avoid this, the contents of the tank should be 
examined at regfular intervals or when the supply is low, 
and the tank drained whenever there is any doubt about the 
quality of the liquid that settles in the lower portions. 

16»— 26 



59. The cause of back firing in stationary engines is in 
most cases due to the delayed combustion of a weak mixture 
containing an insufficient amount of fuel. The result of 
such a mixture is a weak explosion and slow burning, so 
that, during the entire exhaust stroke and even at the begin- 
ning of the suction stroke, there is a flame in the combus- 
tion chamber. The fresh charge will therefore be ignited 
by the flame of the delayed combustion of the previous 
charge ; and, as the inlet valve is open at that time toward 
the air-supply pipe or passage, a loud report will be heard in 
the air vessel or in the space under the engine bed whence 
the air is taken. The remedy for this condition is to 
increase the fuel supply until the explosions become of nor- 
mal strength and the back firing ceases. 

Another cause of back firing may be the presence of an 
incandescent body in the combustion chamber, such as a 
sharp point or edge of metal, a projecting piece of asbestos 
packing, soot, or carbonized oil, and similar impurities 
accumulating in the cylinder. To stop back firing from 
these causes, any projections of metal or other material 
should be removed with a suitable tool, and the walls of the 
combustion chamber made as smooth as possible, or the 
cylinder should be cleared of any deposit of soot or carbon- 
ized oil that may have gathered there. 

Failure of the igniter to fire all charges admitted to the 
cylinder, or improper composition of the mixture resulting 
in the same way, will be indicated by heavy reports at the 
end of the exhaust pipe. One or more charges may in this 
manner be forced through the cylinder into the exhaust 
pipe, and the first hot exhaust resulting from the combus- 
tion of a charge will fire the mixture that has accumulated 
in the pipe and the explosion wU be accompanied by a 
report similar to that of the firing of a heavy cannon. 

60, On account of the shorter time between the opening 
of the exhaust port and the admission of the new charge in 


a two-cycle engine, there is much greater liability to back 
firing in an engine of that type than in a four-cycle engine. 
In a four-cycle engine back firing will occur only when the inlet 
valve is off its seat ; hence, in marine j^ractice, back firing is 
more of an element of danger in four-cycle than in two-cycle 
engines. If there is no check-valve in the carbureter or 
vaporizer, and there is no direct opening to the atmosphere, 
the column of flame that would be blown into a boat 
through a carbureter or auxiliary air supply on account of 
back firing would be particularly dangerous because accumu- 
lations of gasoline vapor, especially in cabin boats, might 
thereby become ignited. 

To be absolutely safe, a marine four-cycle engine having 
a float-feed carbureter not supplied with a check-valve 
should take its supply of air from some point outside of the 
cabin or from the top of the engine, rather than from a 
point near the base. As the use of a check- valve in the 
carbureter would materially reduce the efficiency of the 
engine, it is rarely used. If a float-feed carbureter is used, 
and indications point to imperfect carburization, the carbu- 
reter should be examined carefully. If the float leaks, so 
that the height of gasoline is constantly above the desired 
level, or if the float does not cut off the supply where it 
should, it will be necessary to take the carbureter apart to 
ascertain the trouble, which may be due to a stopped-up 
needle valve or nozzle. 

61. Explosions in the muffler and exhaust piping are 
usually caused by the ignition of the gas accumulating from 
missed explosions due to weak mixtures or faulty ignition. 
They are not usually dangerous unless the muffler is large and 
is weakened by rusting inside or out, as from salt water 
passing through it or from damp salt air, against which it 
seems almost impossible to protect it in a boat. 


62. Explosions in the carbureter are sometimes caused 
by the inlet valve sticking open and permitting the flame to 
communicate from the spark. More often it is due to 
improper mixture, which bums so slowly that flame lingers 


in the cylinder even after the exhaust stroke is completed 
and the inlet valve begins to open. Either a weak or a rich 
mixture will produce this result, though not alwajrs both in 
the same engine. Carbureter explosions are often attributed 
to the exhaust valve closing after the inlet valve opens, or 
to simple leakage of the inlet valve; but these are seldom 
the real causes. 



63. Deflnltlon. — Premature ignition, or preignition, 
while somewhat similar to back firing in its nature and 
origin, manifests itself in a diflPerent way and has a different 
effect on the action of the engine. Premature ignition, as 
usually understood, is the firing of the partly compressed 
mixture before the time fixed by the igniting mechanism. 
Its causes are similar to those that result in back firing, the 
effect being different in that the charge is ignited later 
than when back firing takes place, but before the end of the 
compression stroke. Preignition will cause the engine to 
lose power on account of the maximum pressure being 
exerted on the crank before it reaches the inner dead center 
and thus ha\'ing a tendency to turn it in the >\Tong direction, 
airainst the momentum of the flvwheels. 

64, Causes of Preigrnition. — Besides the causes cited 
in connection with back firing, preignition may be due to 
any one of the following defects: Insufi&cient cooling of the 
cylinder, due either to shortage of cooling water or to the 
fact that portions of the water-jacket become filled vnih 
lime deposits or impurities contained in the water, thus 
interfering with proper circulation; compression too high 
for ilie *:Tade of fuel used ; imp)erfections in the surfaces oi 
I ho piston end or valve heads exposed to the combustion, 
such as s.ind holes or similar caWlies in which a small por- 
tivMi o( the Iniruing- charge may be confined; electrodes or 


other parts of the engine exposed to the burning charge too 
light; or the piston head or exhaust- valve poppet insuffi- 
ciently cooled and becoming red hot while the engine is run- 
ning under a fairly heavy load. 

65. Premature ignition manifests itself by a pounding 

in the cylinder, and, if permitted to continue, a drop in 

speed, finally resulting in the stopping of the engine. It 

vrill also put an excessive amount of pressure on the bearings, 

especially the connecting-rod brasses, and cause them to run 

liot even when properly lubricated. After a shut-down due 

to premature ignition and a short period during which the 

engine is idle, allowing the overheated parts to cool oflF, it 

is possible to start again without difficulty and run smoothly 

until the conditions of load will cause a repetition of the 


66. The remedies to be applied, according to the source 
of the difficulty, are as follows : Increase the water supply until 
the cooling water leaves the cylinder at a reasonable tem- 
perature, which may vary with the fuel used, but which 
should never be over 180° F. Clean the water space and 
ports of any dirt or deposit so as to insure free circulation 
of the cooling water. Reduce the compression by partly 
throttling the air and fuel supply. Plug any sandholes or 
blowholes in the piston or valve heads, and make these sur- 
faces perfectly smooth. Replace electrodes or other light 
parts with more substantial ones, capable of absorbing and 
carrying oflF the heat without becoming red hot. If neces- 
sary, arrange for cooling the piston by blowing air into the 
open end of the cylinder. 

If the head of the exhaust valve becomes too hot, it is a 
sign that it is not heavy enough, and it should be replaced 
by one with a head of sufficient thickness to carry off 
through the valve stem the heat imparted to it by the com- 
bustion. If a small particle of dirt lodges in a remote por- 
tion of the combustion chamber, the richer part of the 
charge may not reach it until the piston has traveled over a 
considerable portion of the compression stroke, and the 


resulting self-igrnition may properly be called preignition. 
It is advisable, therefore, to examine thoroughly every part 
of the combustion chamber and remove any dirt that may 
have lodged there. 

67, Preignition in automobile engines is indicated by 
early ignition with a retarded spark. Usually, the engine 
will continue running for several seconds after the switch 
has been opened. The knock due to preignition has a sharp, 
metallic ring, easily distinguishable from other knocks in 
the engine. Even if ignition is not actually started by hot 
carbon or other cause, the first increase in pressure after the 
spark occurs may produce spontaneous ignition of the mix- 
ture near the heated object, so that the charge bums from 
two or more points at once, thus spreading the flame far 
more rapidly than usual. 

If the engine has two or more cylinders, and only some of 
them incline to preignition, the result is that it is impossible 
to time the ignition correctly for all cylinders. The cylin- 
ders having a tendency to preignition must receive a late 
spark to prevent combustion from being completed too 
early, while the other cylinders will require an early spark. 
It follows from this that it is impossible to get the engine to 
develop its full torque, or turning moment, unless it is run- 
ning so fast that the tendency to preignition may be neglect- 
ed. As the eflPect of preignition is to cause combustion to 
be completed before expansion has begun, it is dangerous to 
run the engine slowly, and this is true even if only one 
cylinder is preigniting. If the engine is running at good 
speed, with an early spark, the symptoms will be those of 
rapid combustion in the cylinders aflFectefl; namely, a hard-' 
ness in the sound of the explosion, without actual knocking, 
while in the other cylinders, if any, the explosion will be 
soft. As the speed of the engine is reduced, and the spark 
retarded to suit, the hard sound of the explosions gives 
place to unmistakable knocking. A good test for preignition 
due to carbon is to start the motor with everything cold, and 
run the car smartly up the nearest hill before the water in the 



radiator has had time to get hot. The bing! bing! bingf 
then is a sure sign. If the carbon deposit is very great, the 
motor may knock when gearing up, if this is done quickly 
with the motor running rather slowly. 

In ^ automobile as in stationary engines, preignition is 
"brought about by incandescent carbon deposits in the com- 
T>ustion chamber, on piston head, or on valves, or by bits of 
loose carbon left after scraping out, etc. It is sometimes 
due to small, accidental projections on the inner wall of the 
combustion chamber or head, due to defects in casting. If 
these are located in the path of the hot gases, it will take 
very little carbon deposit on them to overheat. Preignition 
is also caused by lack of water, resulting in general over- 

It must not be supposed that all carbon deposits are due 
to neglect. Even the most scrupulous regulation of the 
best possible oil, and even the most efficient carbureter, will 
not wholly prevent a gradual accumulation of carbon, but it 
ought not to become troublesome in less than a season or 
two. A high-compression engine will, other things being 
equal, preignite sooner than one with low compression. 

The only remedy for carbon deposit that amounts to any- 
thing is to scrape it out. To do this it may be necessary to 
take off the cylinders, but it may also be done in some 
cases by the use of special forms of scrapers that will reach 
into the combustion chamber through the inlet-valve or 
spark-plug hole. 

If it is impracticable to scrape the cylinders at once, the 
trouble may be evaded after a fashion by running throttled 
and by running on a lower gear at the first symptoms of a 
pound. Increasing 'the richness of the mixture will also 
prevent pounding by making the charges bum more slowly, 
but this brings its penalty by adding to the carbon already 
present. If this trouble is due to chance projections in the 
combustion chamber, these may generally be disclosed by 
an electric lamp and mirror and when the cylinders are 
taken off, the projections can be cut away with a cold 



68. Weak Battery. — Missed explosions may result from 
a weak battery. An open-air test of the spark, by discon- 
necting a cable from one of the plugs or laying a screwdriver 
on the plug binding post, will show a weak spark when the 
battery is weak. It is sometimes difficult to determine 
whether the explosions are missed because the battery is 
weak or because of a loose connection or broken wire some- 
where in the ignition circuits. The only reliable way to 
determine this point, unless one has a fresh set of cells in 
reserve, is to carry a battery tester and test the cells as soon as 
skipping occurs. The battery strength required will depend 
on the character of the coil, but it is not often that a dry cell 
showing less than 5 amperes on short circuit is worth retaining. 

If both sets of dry batteries are so far exhausted that 
neither will work the coil, the two may be coupled in series, 
which will generally make it possible to run the car for some 
miles farther. When home is reached the batteries should 
be recharged or replaced. 

A wet- or a dry-cell battery for supplying the current will 
be exhausted after a certain period of time, and, if handled 
carelessly, its life may fall far below what may reasonably be 
expected. If a wet battery becomes exhausted through 
long service or accidental short circuit in its parts or connec- 
tions, the contents of the jars must be emptied and the 
charge renewed. The manufacturer or dealer in elec- 
trical supplies furnishes full printed instructions with every 
set of renewals for batteries. It is generally false economy to 
try to use part of the old charge. In almost every case it is 
far better to throw away all of the original zincs, oxide 
plates, and solution, rather than to try to rejuvenate the cell 
by adding to or replacing part of its contents. 

69. Current JLeakagre. — Sufficient leakage of current 
to make trouble — but not enough to be observed without 
testing with a magneto — may be due to moisture in the mica 
insulation of the insulated electrode or to abridge of carbon. 


When it is suspected that the trouble is due to either of these 
causes, it is a good plan to dry out the insulation thoroughly 
and clean the lower end with a brush or piece of waste and a 
little gasoline. 

These troubles are more liable to occur when the batteries 
have become weak from use, or so far exhausted that they 
will not give sufficient cturent for ignition. 

70. Testing Batteries. — By using a small electrical 
buzzer or bell each cell may be tested separately, and by 
the tone or sound it can readily be observed whether or not 
the battery needs renewing, as is often the case. A small 
pocket ammeter or voltmeter is very convenient for the pur- 
pose of testing batteries, but each cell should be tested sepa- 
rately, as the pocket apparatus will rarely stand the voltage 
or amperage of more than one cell. Occasionally the buzzer, 
bell, or voltmeter will show one of the cells of the batter)' 
exhausted or dead, and on its removal the battery will show 
sufficient strength for ignition purposes. 

71. Beserve Battery Poiver. — While four or five dry 
cells, when new, will furnish sufficient current for ignition, 
it is customary to install six or even eight cells, so that, when 
they become partially exhausted, or it becomes necessary to 
remove one or two from the circuit, there will be a sufficient 
number left to supply the necessary current. It is, how- 
ever, never safe to depend on a single battery. A reserve 
set of dry cells, carefully wired up, should always be carried 
in a dry box, for frequently when used in a boat the bottoms 
of the dry cells may become damp or the switch is liable to 
be left closed, with the electrodes in contact, with the result 
that, through the short circuit thereby produced, the bat- 
tery will be exhausted and ruined in a very short time. 


73. Broken Spark-Plugr Porcelain. — The breaking 
of a spark-plug porcelain usually results in complete failure 
to ignite the charge in that particular cylinder, ov 


the secondary current shortingr, that is, short-circuiting, 
through the break. The outer end of the porcelain will 
generally be loose when tried by the fingers. 

The usual cause of breaking is screwing the bushing down 
too tight. If the asbestos packing is of uneven thickness, it 
may be necessary to screw the bushing quite tight to prevent 
leakage. Overheating and splashing of water on a hot porce- 
lain will also cause breaking. Remedies for such trouble are 
found in using new asbestos packing and in providing pro — 
tection from water, etc. 

73. Soot on Spark-PIufiT Porcelain. — Soot on th^ 
spark-plug porcelain will cause misfiring, or total failure to 
ignite, when the battery is of proper strength and the 
vibrators on the coils are working properly. If the engine 
has more than one cylinder, probably one or more will be 
found to be working properly, and the one with the defective 
spark plug may be located by holding down one coil vibrator 
after another, thus stopping explosions in each cylinder in 
turn, until the vibrator feeding the inactive cylinder is 
reached. By listening carefully to the exhaust, when it is 
known that one cylinder is misfiring, it will be observed 
that, when the vibrator of an active cylinder is depressed, it 
will cause a noticeable break in the cycle of explosions 
When the vibrator of an inactive cylinder is depressed, no 
such break will be noticed. It is, of course, necessary to 
know which cylinder is fed by each vibrator. A spark plug 
may be sooted to the extent of short-circuiting when in the 
cylinder, and yet spark properly in the open air, as the elec- 
trical resistance of air increases greatly when the air is com- 
pressed. If a plug is slightly sooted, and there is uncertainty 
as to whether the trouble is due to the soot or to something else, 
insert a fresh plug, substituting one from another cylinder, if 
there are no spare plugs at hand, and note the result. A primary 
sparker coated with soot will act nearly the same as a sooted 
plug; the extra current producing the spark will leak away 
lo a considerable extent through the carbon instead of pro- 
ducing an effective spark. 


The causes of sooting are too much lubricating oil, inferior 
oil, or a too-rich mixture. The overrich mixture will 
deposit pure black soot, whereas an excessive quantity of 
lubricating oil will produce a rusty-brown deposit. Inferior 
oil may produce almost any sort of a deposit, according to its 
quality. A great excess of either good or bad oil will not 
burn completely before it reaches the plug, and will deposit 
on the latter a greasy mixture of carbon, tar, and oil. An 
engine receiving oil in such quantities as this will foul the 
plugs within a mile or two, and energetic measures must be 
taken to get rid of the surplus oil. 

If the sooting is not excessive, and if the cause is removed, 
the plug may be kept in action without cleaning by the use 
of an auxiliary spark-gap device, which may be connected 
to the binding post of the plug. The soot will then be 
gradually burned off. 

74. Jjealcy Spark Pluitc. — If the leak is between the 
plug shell and the cylinder, it will be denoted by the hiss of 
escaping gas on the compression and power strokes. The 
plug may be screwed tighter or a new gasket used. If the 
leak is through or past the packing inside the plug, the same 
hiss will be heard, and in addition the outer end of the ])c)rcc- 
lain will show traces of soot after the gases have been leaking 
for some time. If the bushing of the plug has been screwed 
as tight as is prudent, with regard to the safety of the porce- 
lain, it will be necessary to repack the phig. A plug allowed 
to leak to any noticeable extent will overheat, cracking the 
porcelain or burning the screw threads. 


75. Poor Contacts. — In order to obtain a spark of mtf- 
ficient size in the combustion chambers of engin(»H cfpilppod 
with the make-and-break system of igniticMi, it is nrccssiiry 
that a good contact l)e made between tlie tw«» elcM'tHKlrs nf 
the igniter plug Ixifore ihcy separate. Th«* cnrnMH pnHsrM 
through the bearing of the movable eleelrode, and, if thn 


contact between the bearing and the stem of the electrode 
is poor, only a weak current can find its way to the point of 
contact, resulting in a feeble spark that may be too weak to 
fire the compressed mixture. Poor contact of the electrode 
may be caused by an inferior quality of lubricating oil form- 
ing a thin layer of carbon (which is a poor conductor) on the 
stem, or it may be due to wear of the bearing and a loose fit 
of the stem. To prevent wear on the stem and bearing it is 
important that the seat of the electrode be kept tight, so as 
to prevent the heat of the burning charge from reaching 
the stem and to keep it as cool as possible. This will aid 
in keepingthe stem well lubricated, as the oil cannot be burned 
and form the objectionable carbon deposit. At the same 
time, the electrode will move easily without sticking, which 
is essential to a prompt separation of the two contact points. 

76, Short Circuits, — A ground or short circuit of 
the current is often responsible for difi&culties or failures of 
the igniter. This may be caused by carbonized oil on the 
exposed surface of the insulators, or by dampness between 
the mica washers if these are used for insulation. By pla- 
cing the igniter plug in a warm place and drying it thor- 
oughly, a short circuit of this kind can often be remedied. 

77. Slioit-Tline Contact. — The length of time during 
which the electrode points are in contact has a decided 
effect on tlie size of the spark. To test whether the contact 
is of sufficient duration, hold the two points together by 
exerting pressure by hand on the movable electrode. If 
this is found to cure the trouble, it is a sure indication that 
the contact is too short, and the parts that make the contact 
must then be adjusted so as to prolong the time of contact. 
This is accomplished in some igniters by increasing the ten- 
sion of the igniter contact spring, while in others the 
adjustment is made by changing the relative positions of the 
interrupter lever of the movable electrode and the blade of 
the igniter lever that operates it and presses it against the 
fixed electrode. 


78. Dirty Contact Points. — The contact points must 
be kept free from rust or moisture, both of which will inter- 
fere with the making of a bright spark. An occasional 
cleaning of the points by the use of emery cloth is advisa- 
ble. Moisture on the electrode may be caused by condensa- 
tion of the exhaust gases if the electrodes are very cold, 
which is likely to be the case in freezing weather before 
starting. The remedy is to heat the igniter plug thoroughly 
l)ef ore attempting to start the engine. If moisture deposited 
on the electrodes is the result of a leaky packing or gas- 
Icet, or of a defect in the cylinder, allowing water to enter 
the combustion chamber from the surrounding jacket space, 
it is possible to overcome this temporarily by wiping the 
interior of the combustion chamber dry with cotton waste or 
similar material. In this way the water may be kept away 
from the igniter long enough to get the engine started; but 
the real source of the trouble should be remedied at the 
earliest opportunity. 


79. Vibrator Out of Adjustment. — If the vibrator 
sticks, the symptoms will be erratic firing; few or no explo- 
sions will be missedi but the impulses will sometimes be very 
weak because the sticking causes a very late spark. Too 
light a pressure of the contact screw will cause the engine 
to run weak and fitfully; too much pressure will exhaust 
the battery rapidly. Either condition will manifest itself to 
the practiced ear by the sound of the vibrator. Poor firing 
may be caused also by pitting of the contact points. This 
may be remedied by filing the contact points, which should 
bear squarely against each other, and readjusting the spring 
and contact screw. 

80. Defective Condenser. — A condenser short-cir- 
cuited or having one of the connections broken will show it 
by sparking at the trembler and timer contacts, and by rapid 
burning of the metal where the spark occurs. The only 
remedy is to send the coil to the factory for repairs. 


81. Short-circuited Coll. — A spark coil may short 
circuit from breakdown of the insulation in either the pri- 
mary or secondary winding. The sytnptom is a poor spark 
or none at all, and refusal of the vibrator to work, even 
with a good battery. The only remedy is to send the coil to 
the factory for repairs. The spark coil must be kept in a- 
thoroughly dry place, as moisture will surely cause trouble^ 
and will interfere with the current passing through the coil_ 
to the engine. If the spark coil is found to be moist, it cam^ 
generally be put in serviceable condition by drying it in aim^ 


83. Break In Primary Circuit, — The symptoms pro- 
duced by a break in the primary circuit, which includes all 
wiring except from the coil to the plug, or from a secondary 
distributor to the plugs, are intermittent or complete failure 
to spark, according to whether the connection is intermit- 
tently restored by vibration or is wholly broken, and failure 
of the vibrators to work. 

The almost invariable cause of breaks in the primary cir- 
cuit is vibration, which will loosen nuts on binding posts and 
break wires in places sometimes quite unexpected. 

The first step to be taken in remedjring the trouble is to 
test every binding post, usually by shaking the wires with 
the fingers. If this does not disclose the trouble, hunt for a 
break in the wiring. It will generally be found close to a 
binding post, switch terminal, or other connection, where 
the bending due to vibration is most severe. As a last 
resort, close the switch, open the compression relief cocks, 
retard the spark, and turn the crank so as to make contact 
at the timer; then with a length of spare wire shunt suc- 
cessively each wire in the primary circuit by touching the 
ends of the spare wire to the ends of the regular wire until 
you have found the one with the break. The spare wire 
thus bridges the break in the regular wire and causes the 
igniter to operate. Then hunt down the break in that par- 
ticular wire, or take it out and put in a new one. If the 


wire has a soldered joint, it will be brittle at that joint and 
may have broken ; or, it may have been fastened in such a 
manner as to strain it; or a badly made and twisted joint 
may have worked loose. Note that the break may be 
between the timer and the coil, in which case it will aflFect 
one coil only. A wire is quite likely to break inside its 
insulation, or just at the point where the insulation 
has been stripped oflF. A troublesome kind of break is 
that which is opened only by the vibration of running, and 
is closed by the elasticity of the wire or insulation, or by the 
weight of the battery cells or other connected members, 
when the car is stopped. A great deal of patience is some- 
times needed to trace a break of this sort. 

83. Short Circuit or Ground In Primary. — A short 
circuit or ground in the primary conductor is not a common 
trouble, and it can be avoided by the most ordinary care in 
insulating the primary. The symptoms are much like those 
due to a broken wire, but an ammeter test close to the bat- 
tery will show that current is flowing. It is most likely to 
occur by the chafing through of the insulation of poorly sup- 
ported wires, or by neglect to insulate properly some home- 
made attachment in the circuit. It may be due to contact 
of the dry primary cells or bolts passing through the bat- 
tery box. A little patience is all that is needed to locate 
the trouble. 

84. Broken Secondary Cable. — As the secondary 
cables are short and thick, a break in them is an unusual 
fault. If the break is not too great, the current will jump 
it, and the sparking there will at once disclose the trouble. 

85. Grounded Secondary Cable. — A grounded sec- 
ondary cable, which is indicated by failure to spark when 
the vibrator is working, is generally due to the chafing 
through of insulation on a badly supported cable. Some- 
times it is due to rotting of rubber insulation by heat and 
oil. If the secondary cable has been spliced and taped, the 
current will go thr' unless the cable is well out 


of the way of grounded metal work near the splice. Such a 
cable may give a spark at the plug as well as at the ground, 
which will soon exhaust the battery. 

The roadside remedy for a grounded secondary wire is to 
tie the cable clear of the metal work. The permanent reme- 
dy is to put in a fresh cable, adequately protected by fiber 
tubes or other insulating supports. A cable with a var- 
nished exterior is the best, as it resists oil. A rubber-cov- 
ered cable exposed to oil may be protected by a coat of 
shellac or a layer or two of tape. 

86, lioose Electrical Connections. — To obviate fail- 
ure to start because of loose or defective electrical connec- 
tions, the ignition mechanism should be tested carefully. 
With the make-and-break system of ignition this is done by 
disconnecting the wire from the binding post or nut of the 
insulated electrode while the electrodes are in contact, and 
then snapping the end of the wire across the binding nut of 
the insulated electrode. If a good fat spark is produced 
when the wire slips off the nut, thus breaking the circuit, it 
is evident that the circuit is not defective beyond the igni- 
ter and that the contact between the electrodes is good. 

If, with the wire connected to the insulated electrode and 
with the igniter contact points separated, a screwdriver 
were placed so as to make contact with the binding nut of 
the insulated electrode and with a capscrew, studbolt, or some 
bright part of the engine, the production of a spark when the 
contact between the screwdriver and the nut of the insulated 
electrode is broken would indicate that no short circuit 
exists in the igniter. If, however, no spark should be pro- 
duced on breaking contact with the screwdriver, it would 
indicate the existence of a short circuit that should be found 
and eliminated. Should a spark be produced on breaking 
contact with the screwdriver when the two electrodes are in 
contact, it would be evidence of poor contact between the 
points. No spark will appear on breaking the circuit when 
the contact between the points is good. 

The break of a wire inside the insulation, while not of 



frequent occurrence, is harder to locate than a loose electrical 
connection. In cases where it appears impossible to find 
the trouble, the existence of the broken wire may be deter- 
mined by running a temporary wire from the coil to the 
engine, spark coil, switch or battery, as the broken wire 
may be so situated as to show occasionally either an open or 
a closed circuit. 

A loose rocker-arm fastened to the movable electrode will 
sometimes give considerable trouble that will be found dif- 
ficult to locate. A very little lost motion where the shaft is 
small is increased rapidly; and, as soon as the shaft becomes 
the least bit loose, the pounding to which it is subjected will 
caUse it to loosen very quickly. 

Switches should have good, clean contact points, otherwise 
leaks will affect both systems of ignition. 


87. Timer Contacts Rougrhened by Sparkingr* 

Trouble due to roughening of the timer contacts by spark- 
ing is likely to occur in any timer in which the contact 
segments are inserted flush with the insulator barrel or 
internal ring, instead of projecting therefrom. 

The symptom produced by roughened contacts is irregular 
firing, due to jumping of the contact roller or fingers. This 
is not noticeable at low speeds, but becomes marked as the 
speed increases. The remedy is to true the insulator ring 
and segments in a lathe, and, if necessary, put in a new 
roller or contact fingers. 

88. Wabbling Timer. — Some timers have their sta- 
tionary portion supported on the shaft by a very short bear- 
ing that quickly wears loose and allows the stationary 
portion to wabble out of its correct plane. This will cause 
irregular firing or even misfiring. One may easily deter- 
mine whether the cause of the misfiring is here or elsewhere 
by steadying the timer with the hand. The remedy is to 
bush the bearing, and, if possible, to make it longer. 


89. Incorrect Tlmingr. — With marine engines having 
make-and-break ignition mechanism, even if the current is 
sufficient and there are no leaks, the time of contact may be 
too short, may be made at the wrong point in the stroke, or 
may be broken when it should not be, owing to incorrect 
timing. The timing may be tested by turning the fly- 
wheel carefully in the proper direction, and noting when the 
contact is made and at what point the spark occurs. By 
scratching the flywheel at these points, when the engine is 
nmning satisfactorily, it is always a simple matter to correct 
any trouble in the time of sparking. Raising or lowering 
the igniter pin without following any particular rule or with- 
out knowledge of what one is doing is very bad practice, 
and is more likely to aggravate than to remedy the diffi- 
culty. It is evident that, in multicylinder engines, it is 
quite important that there should be for each cylinder the 
same relative time of making and breaking the contact, with 
the same length of time in contact. 



90. Habitual feeding of an excess of lubricating oil 
to the engine will gradually clog the muffler with a mixture 
of carbon and half -burned oil, which will reduce the power 
of the engine and be very difficult to remove. 

The symptoms produced are loss of power and inability to 
speed up the engine when the mixture, compression, valve 
timing, and ignition are known to be good; if the exhaust 
pipes can be disconnected, the engine gives its full power at 

To remedy the trouble, take off the muffier and saturate 
the interior with kerosene, after which the deposit can 
usually be knocked, scraped, or shaken out. 



91, Probably the most dangerous trouble eicperienced 
with marine engines is due to leaks in the gasoline tanks or 
piping. They are more likely to occur at unions than any- 
where else, and all joints and fittings should be soldered or 
brazed, as well as screwed. Hence, the piping is not liable 
to be broken at the threads, reinforced as they are with 
solder. Unions should be very heavy, and should be exam- 
ined for leaks carefully and often. Do not use a light or 
match, but rub the finger around the joint, when, if there is 
a leak, it may be detected by the odor that will remain on 
the finger. Small leaks may be stopped temporarily by 
means of cloth and shellac or soap. Insulating tape will be 
found useless for the purpose, as the gasoline is a solvent 
for the insulating material. 

A good cord closely and tightly wound will be found serv- 
iceable. Shellac and cloth bound on tightly and allowed to 
dry with no gasoline in the pipe will be found very effective 
in stopping leaks. It is necessary to be extremely careful 
of fire in the presence or suspected presence of gasoline, 
particularly when in the form of vapor and mixed with air. 


93. The exhaust gases from stationary gas or gasoline 
engines contain a certain amount of moisture, part of whicli 
is condensed and deposited in the exhaust pipe or muffler, 
where it may become a source of trouble if no provision has 
been made to drain these connections properly or if the 
draining devices accidentally fail to perform their functions 
as exx)ected. Especially during cold weather, when the 
condensation in the exhaust connections is greater than at 
more moderate temperatures^ it is advisable to inspect 
closely the condition of the drain cocks. If neglected, the 
level of the water in the muffler may rise to such an extent 
as to prevent the exhaust gas from being expelled, first 
causing loss of power and finally stopping of the engine. 


In engines in which the governor acts on the exhaust valve, 
and this valve is kept open while running under light load, 
the trouble from water in the exhaust, when no charges 
are admitted to the cylinder, is naturally intensified, on 
account of the fact that a portion of this water is drawn 
into the cylinder while the valve is open during the suc- 
tion stroke. The presence of water in the exhaust connec- 
tions is usually indicated by steam or water spray issuing 
from the end of the exhaust pipe. 

As before stated, water is frequently used for deadening 
the noise of the exhaust by introducing it in a small steady 
stream into the exhaust pipe and allowing it to be carried 
off in the shape of vapor or spray with the exhaust gases. 
In such cases, the draining devices require particular atten- 
tion, because, in the case of failure to have a free outlet to the 
drain for any part of the water not carried off with the exhaust, 
the accumulation of water would in a short time be sufficient 
to stop the engine. 


93. An accumulation of water in the cylinder — a con- 
dition encountered more or less frequently in marine prac- 
tice — will effectually prevent a gas engine from starting. 
The water may get in through the exhaust pipe because 
the installation is faulty, because the exhaust extends below 
the surface of the water, or because there is a leak due to a 
crack in the cylinder or to a broken and imperfect gasket 
between the cylinder and the water-jacket. Running the 
exhaust cooling water into the engine exhaust is a frequent 
source of such trouble. 

Provided the trouble from water in the cylinder is not due 
to leaks the remedy is to remove the water entirely, by 
means of absorbent materials, through any openings there 
may be in the cylinder. The insulated electrode should then 
be carefully dried out, the defect in installation remedied 
by changing the exhaust piping to drain outboard, and, if 
exhausting below the surface of the water, a vent provided 
in the highest part of the exhaust piping. 



94. If the connection between the governor and the 
throttle is too long, the throttle may fail to close until the 
governor balls have been moved out to an excessive extent 
by the speed of the engine. In an old engine, wear of the 
connecting links may produce the same result. Sometimes 
there is an adjustable screw and nut connection between the 
governor and the throttle, and this is easily adjusted. 
Sometimes, however, it may be necessary to bend the rod 
connecting the two. The throttle should be opened, and its 
position when barely open should be marked in such a way 
that it will be known when the throttle is reassembled. Then 
the engine should be run idle and the position of the gover- 
nor lever noted when the engine is running at the speed at 
which it is desired that the governor should act. With these 
particulars known, it is easy to shorten the rod to bring the 
throttle to the desired position. It should be remembered 
that a very slight opening of the throttle is sufficient to keep 
the motor running 





96. It is practically impossible to turn a piston in a lathe 
so as to fit the cylinder in such a manner that the engine will 
run properly even under a partial load. The best that can be 
done is to have the cylinder bored slightly larger at the end 
nearest the crank-shaft, so that the piston can be pushed in 
easily from this end and will fit rather snugly at the other 
end near the combustion chamber. To put the piston and 
cylinder in condition to stand constant running under load 
necessitates filing the surface of the piston by hand, as fol- 
lows; See that both cylinder and piston are thoroughly clean 
and free from dust or filings. Apply a liberal amount of 
lubricating oil, place the piston in the cylinder, and attach 
the connecting-rod to the crank-shaft. Start the engine, and 
let it run idle for a while. As soon as the heat of the explo- 
sion causes the piston to expand, it will begin to stick in the 
cylinder, as the water-cooled walls of the cylinder do not 
expand to the same extent as the piston. The sticking is 
manifested by a pounding or knocking sound caused by 
the very slight amount of play that necessarily exists in the 
bearings of the connecting-rod at both the crankpin and the 
piston end. As soon as this pounding appears, apply more 
lubricating oil to the piston, and let it run for a few minutes in 
this manner, without any load. Then stop the engine, take 
out the piston, and wipe it dry. The portions of the piston 
that bear hard against the cylinder will be indicated by 
glossy spots, which should be carefully filed \\ath a smooth. 
Hat file, removing ^)iily a little at a time. To facilitate filing, 


remove all traces of lubricating oil by means of kerosene. 
After filing the piston surface in this way, clean the piston, 
put it back in the engine, and start up again. It will be 
noticed that it is now possible to run the engine for a longer 
period without any pounding in the cylinder and perhaps to 
be able to put on a light load for a short time. Do not 
keep the engine running with any load for any length of 
time, so long as there is any pounding noticeable. This 
operation may have to be repeated from four to six times, 
depending on the skill of the operator, before the engine can 
run steadily with the usual maximum load. 

These instructions apply also to cylinders that have been 
rebored and fitted with new pistons, as the conditions in this 
case are the same as in a new cylinder. 

96. The piston rings also require fitting in a similar 
manner, and in this connection the following points must be 
observed : Before placing the rings in the grooves, each ring 
should be tried, to ascertain that it fits in the groove for 
which it is intended. If the ring is found too thick, place it 
on a straight board, and hold it in place by fastening three or 
four nails within the ring, driving them down until the heads 
are slightly below the top of the ring. Having thus secured 
the ring on the board, file it carefully and reduce its thickness 
so as to get an easy sliding and uniform fit in its groove. 

The rings can now be put in place by opening them and 
slipping them over the piston from the closed end. In doing 
so, the rings should be expanded and twisted as little as pos- 
sible. The first ring must be placed in the groove farthest 
away from the closed end of the piston, the others following 
in order. If, after runnirfg the engine with new rings for a 
short time, the rings show that they bear hard and unevenly, 
the hard-bearing portions must be touched up with a fine 
file. Should it become necessary at any time to replace a 
broken ring located between other rings, the use of small pieces 
of thin sheet tin will be found of advantage. They are 
slipped in between the inside of the ring and the outside of 
the piston, at a convenient point of the circumference, so as to 


keep the ring evenly expanded and enable it to be moved 
laterally over other rings already in place to the groove for 
which it is intended. Having reached its groove, the pieces 
of tin are withdrawn, and the ring is allowed to enter the 

A ring that, from undue expansion or twisting, has lost 
its original diameter will not bear evenly and vdll wear out 
the cylinder in a short time, causing leakage and loss of 


97. Neglect in draining the cylinder jacket when stop- 
ping the engine after the day's run may result in cracking 
the outer shell in cold weather, owing to the freezing of the 
water. It is very seldom that the inner cylinder is damaged 
in such a case, but if it should happen to be injured, the 
casting is generally rendered useless and must be replaced 
with a new one. The outer shell, being much lighter than 
the cylinder itself, provides a safeguard against damage to 
the latter, and in most cases, if the cylinder and jacket are 
cast in one piece, it will be possible and economical to repair 
the cracked shell. 

The following directions arc intended to cover repairs for 
various kinds of cracks, and apply to cracks in cylinder 
jackets proper, as well as to cracks in the outer shell of cyl- 
inder heads or valve casings of larger sizes. In large cast- 
ings it will pay to repair the part, rather than replace it with 
a new one ; but with small castings it may be found to be more 
convenient and cheaper to replace the heads or casings 
with new ones. 

Fig. 4 {(i) and (d) shows a cylinder, the outer shell of 
which has been burst bv frost. The crack a b extends only a 
portion of the entire length. After the ice has been thawed 
and the jacket emptied, the first thing to do is to drill two 
holes a and b, ahotit \ inch in diameter, at the ends of the 
crack. The purpose of these holes is to prevent the crack from 
extending any farther on account of the chipping necessary 




ri the next operation. Then take a chisel about -^ inch to \ 
rxch wide and cut a groove along the line of the crack, dove- 
^led as shown at c in the sectional view of the cylinder and. 
^cket, Fig. 4 (d), the groove being widest at the bottom. 


Fk;. 4 

Next secure a piece of \ inch round copper wire, well annealed, 
and hammer it tightly into the groove. By careful calking 
a crack of this nature can be made perfectly tight. 

98.* Fig. 4 (a) also shows a crack de extending from one 
of the water ports to the outer end of the cylinder. In such 
a case, it will be necessary to shrink a steel band / on the 
end of the cylinder, before the crack is chipped out and 
calked in the manner just referred to. Use a flat steel band 
about \ inch by f inch, and be sure that the finished end of the 
cylinder projects about ^ inch beyond the band when in 

If the crack extends over the entire length of the jacket, 
as shown at ^/f, it will require additional bands i and/ as 
shown. If the cylinder has finished collars at the ends, as is 
frequently the case, it will not be possible to slip the ringj 
over the end of the cylinder into its proper place, unless an 
auxiliary band >fe, open to the extent of about \ inch as 
shown at /, is first placed on the cylinder. This band ^ must, 
of course, be thick enough to make up the difference in 
diameter of the cylinder body and the finished collar. In 
shrinking rings on a cylinder, they should be heated to a dull 
red heat and must be handled dexterously, as the cooling 
takes place rapidly and the ring may shrink so as to stick 


before it reaches its position if not applied quickly. After 
the bands have been put in place and have been found to be 
tight, the cracks should be grooved and calked as directed. 

If a crack should devejop in the surface of a joint between 
the cylinder and one of the valve casings attached to it, and if 
this crack crosses the port through which the entering charge 
or the exhaust gases pass, as shown at ;//;/, Fig. 4 (a), it \^*ill 
be practically impossible to repair the casting in such a plan- 
ner that a packing can be made to stand, and the only remedy 
is to replace the damaged part with a new one. 

99. Another method of repairing a short crack in the 
surface of the jacket wall consists in applying a piece of 
steel boiler plate, about -1^ inch thick. Before putting on the 
plate, two \ inch holes should be drilled at the ends of the 
crack, to prevent it from going farther, and a V-shaped groove 
cut along the crack from end to end. The plate must be bent 
so as to conform to the shape of the cylinder jacket. A pack- 
ing of thin asbestos wick soaked in white-lead paste is now put 
in the V-shaped groove, after which a packing of sheet asbestos 
the size of the plate and dipped in water is placed over the 
surface to be covered by the plate. Now apply the plate, 
which is held in place by a number of \ inch to |- inch 
screws, the size of the screws depending on the thickness of 
the water-jacket. The screws should be about 1 inch apart, 1 
inch on each side of the crack ; and, if possible, the tapped 
holes in the jacket, in order to prevent water from leaking 
past the screws, should not be drilled all the way through. 
If the jacket is so thin as to make it necessary to drill the 
holes all the way through, each screw head must be packed 
with hemp or asbestos soaked in white lead. 

100. An automobile-engine water-jacket split by freez- 
ing is also sometimes repaired by the following methods: 
If the crack is very small it may be rusted up. For this pur- 
pose, a saturated solution of salammoniac is made and 
poured into the jacket. A plug, screwed into one of the 
water openings, is drilled and lapped for a small tube, by 

§ 2-t 




which air pressure is put on the liquid in the jacket by means 
of a tire pump. The cylinder is so laid that the crack is at 
the bottom, and after several hours it will be found that the 
edges of the crack have rusted solid from the action of the 

Another method of closing a crack is that shown in Fig. 5. 
The process is to drill and tap a series of | or ^ inch holes 
as close together as practicable for 
the entire length of the crack, 
the first and last holes being at 
the extreme ends of the crack, in 
order to prevent it from extending 
farther. Thesis holes are plugged 
with cast-iron plugs turned and 
threaded for the purpose, and the 
job is completed by rusting in 
with the salammoniac solution as 
just described. When brazing 
facilities are available, it is much ^ 
better to braze a cracked cylinder 
than to try rusting it, as the chances of securing a permanent 
repair are much better. 



PlO. 6 



lOl. The breaking of the studs or bolts that hold the 
connecting-rod box to the rod will often wreck an engine, 
involving the breaking beyond repair of the piston, cylinder, 
and even the bed. As the bed is usually a rather costly part 
to replace, it is frequently found possible to repair it with the 
aid of a strong steel rod properly applied. 

A break repaired in this manner is shown in Fig. 6. It is 
possible to make this kind of repair only when there is a 
clean separation of the casting in two pieces; if the bed is 
broken into a number of small pieces, it must be replaced ^nth 
a new casting. 


To repair a bed, as shown in Fig. 6, first be careful to 
preserve the two pieces so that they will fit exactly when 
put together, using every precaution against careless hand- 
ling and further damage to the surfaces that form the joint 
Then investigate and find the best way in which the steel 


Pig. 6 

rod should be run so as to take hold of the strongest avail- 
able part of the bed. 

The figure shows the rod running inside of the double wall 
casting, a 2-inch rod being used in a space 3 inches wide, and 
being secured by two nuts at each end. The line ab 
indicates the break of the bed casting. At c and d are cast- 
iron washers made to conform to the shape of the casting and 
providing a straight surface for the nuts of the bolts e to rest 
on. It is important that the nuts should bear squarely 
against these washers to avoid any excessive stress on the 
bed casting. Jamb nuts or some other locking device must 
be provided to prevent the nuts that hold the bed together 
from becoming loose as a result of the shocks and jars to 
which the casting is subjected while the engine is running. 
A frequent inspection of the tightness of the nuts is 


102, It is not often that inlet valves must be 
reground, because they remain comparatively cool under the 
influence of the incoming charge, and, moreover, the seats 
are not exposed to the erosion of burning gases. Exhaust 
valves, on the other hand, require regrinding at interv^als, 
depending somewhat on the temperatures in the cylinder, 
and to a large extent on the material of which the exhaust 


valves are made. Ordinar}' mild-steel valves must be 
regTound quite frequently. A much better material is an 
alloy of nickel and steel containing a high percentage of the 
former metal, usually about 25 per cent. Such an alloy as 
this has a very small coefficient of expansion, and is less 
subject to erosion due to the heated gases. Moreover, it is 
not liable to warp out of shape. 

For large engines, and occasionally for small ones also, 
cast iron has been found to be a very good material for the 
exhaust valves. If cast iron is used, the stems and heads 
are made separate; the stems are made of steel, and the 
heads are riveted on the stems. The only drawback to cast 
iron for this purpose is that it has not the strength of steel, 
and the valve head must be of unusual thickness, which, of 
course, adds to the weight and inertia of the valve. 

103. Inlet and exhaust valves are reground with emery. 
If an exhaust valve, the spring is first slipped off to make 
sure that there is no sidewise pressure on the stem to pre- 
vent a true bearing of the valve on its seat The emery is 
mixed with oil until it forms a paste, and is applied freely 
to the surface of the valve and its seat. Extreme care must 
be taken to prevent any of the emery from getting into the 
interior of the cylinder, where it would quickly ruin the pis- 
ton and the cylinder walls. In some cases, a plug of waste 
can be thrust into the valve chamber between the valve and 
the piston; but, if the chamber is not long enough for this, 
the work will have to be watched carefully, using an elec- 
tric light, if necessary, to see that none of the paste works 
away from the valve toward the piston. 

104. If the valve seat is badly out of true, the opera- 
tion of grinding may be begun with emery of medium 
coarseness; but this is seldom necessary, for the reason that, 
before the valve had reached such a condition, the cylinder 
in question would have lost almost all of its power. In any 
case, the work is finished with fine flour of emery. Tho 
emery being applied, the valve is set into its place in tho 
valve seat, and a screwdriver is used in tho slot in tlio vaUv 


head to rotate the valve, which should be worked by quar- 
ter-turns back and forth with moderate pressure, and should 
be lifted at frequent intervals to allow the paste to work in 
between the valve and its seat. In order to grind the 
valve evenly all around, it should occasionally be advanced 
a quarter- turn, and the grinding-in process continued. 
When the grinding is almost finished, the pressure should 
be comparatively light. 

If the valve has been pitted, it will not be necessary to 
grind it until the pits have entirely disappeared, so long as 
there is a good bearing around them. 

When the work is finished, the ground portion of the 
valve should have a smooth, dull appearance, and neither the 
valve nor its seat should at any point be bright, as this 
would indicate that metal had been rubbing on metal with- 
out emery between. 

105. After the valve has been reground several times, 
it is likely to have settled so much lower in its seat as to 
cause the valve stem to remain in contact with the push rod 
when the valve is supposed to be seated. When the valve 
is closed, the clearance between the valve and the push rod 
should be fully equal to the thickness of an ordinary visiting 
card. If the distance is less than this, any slight irregular- 
ity in the cam, or some slight springing of the metal parts 
when the engine is running, might bring the valve stem and 
the push rod together and cause the valve to be opened 

106. In an old motor it may be found that the bushing 
or sleeve in which the valve stem runs is worn to such an 
extent as to permit considerable sidewise movement of the 
stem. A valve in this condition will still operate if it has 
been carefully ground, but it is likely to need grinding much 
oftener than if it were truly guided by its bearing. It 
should never be ground with the spring washer merely 
blocked up; the ^spring should in each case be wholly 





107. When a babbitt-lined bearing becomes over- 
heated and the trouble is not noticed in time, the soft metal 
of the lining, which may have a tin or a lead base, will melt 
and run out of the box. While in some engines the Babbitt 
metal is cast directly in the rough bearings of the engine 
bed, it is the general practice in a first-class engine to bore 
out the bearings in the bed and fit them with cast-iron or 
bronze boxes lined with Babbitt metal. 

If the journals of the shaft are in good condition after the 
metal has been melted and run out of the box, the method 
of rebabbitting the bearing is the same as was followed at 

Fig. 7 

the time the box was made at the factory. To reline the 
box in such a case, proceed as follows: Remove all traces 
of the original lining from the box. While melting the new 
metal in the ladle, place the box on its end on a flat-finished 
surface, and insert an arbor, from ^ ^^ i ^^^^ smaller in 
diameter than the journal, in the center of the box, being 
careful to have an evenly divided space all around the out- 
side of the arbor. The box a being made in halves, as 
shown in Fig. 7, place shims b, b made of cardboard -jV inch 
thick between the joints, having the shims extend well into 
the space around the arbor so as to allow only a thin strip of 
the Babbitt liner c to connect the halves of the lining, in 


der head to the cylinder, screw the nuts on the studs, a^ 
tighten them gradually and evenly. After everything la ; 
been put in order, start the engfine and run it under a li^"^ 
load or idle, until it begins to warm up, when it is fou^r; 
that the nuts can be tightened up still more. This should t 
done promptly, as neglect to take up any expiuision by thi 
heat of the combustion may cause the new packing- tc 
become leaky soon after it has been put in. 

111. While the packing surfaces must be true and 
straight, it does not follow that they should be as smootii 
as glass. Experience has shown that a grooved packing- 
surface gives much better results than a perfectly smooth 
one, although many manufacturers seem to take great pains 
to make the packing surfaces as smooth as possible. In 
many cases, troublesome joints have been permanently 
cured by the judicious application of grooves in the metal 
surfaces. The packing fills the grooves and prevents the 
escape of gas between the packed surfaces. Fig. 8 shows, 
in dotted lines, the positions of the grooves c, which in small 

^ surfaces may be -^ inch deep and 

y? — j-i— — ~- , ^ _^ jjj^jj wide. On circular sur- 

■ faces, such as the packing surface 
] between the cylinder and the cyl- 
inder head, shown in Fig. 9, the 
grooves should be cut concentric, 
and should not come opposite each 
other; biit, when placed together, 
the groove a in the cylinder 3 should be half way between 
the grooves in the head c, as shown, 

lis. Whenever possible, the edge of the packing should 
be protected against the pressure by a projecting rim J, that 
enters the end of the cylinder, as shown in Fig. 9. If no' 
•originally provided by the maker of the engine, it will pay the 
user to have the rim attached by riveting it to the cylinder 
head, in case of persistent trouble with the packing of this 
joint. The depth of the projection </ should be about ^ inch, 
and it should fit rather snugly in the bore of the cylinder, 


but not so that much force will be required to insert the 

113. As the material employed for gaskets is usually 
ssbestos alone, or asbestos, wire gauze, and graphite or similar 
filler, a knife or pair of scissors makes very little impression 
K>n it; but it can be cut out very readily if laid on the cylin- 
der head and carefully cut around on the outside with a 
light, flat-faced, round-peen hammer. The holes can then 
also be cut with the round peen. Great care should be exer- 
cised not to pull out any wires from gaskets in which wire 
gauze is used. The wires should be cut off very carefully. 

If the material used is ordinary asbestos paper -j-^^, ^, -^^^ 
or even -^ inch thick, it should be thoroughly soaked with 
linseed oil, either raw oi; boiled, and dusted carefully with 
powdered or flaked graphite, or with graphite foundry 
facing that contains talc, etc. , which is a very good substi- 
tute. It is a good plan to let this dry a little while in the 
air, when it becomes much tougher. It should not, how- 
ever, be allowed to get too dry. When put in place, the hold- 
ing nuts should be" screwed down carefully, going over them 
several times and screwing down opposite nuts instead of 
adjoining ones. The engine should then be started and run 
a few minutes, with the compression relieved and the circu- 
lating water turned off, in order to heat up the engine and 
assist in dr3dng out the oil or any dampness in the gasket. 
The nuts should then be tightened carefully, when the water 
may safely be turned on. If these directions are followed 
closely, and the gasket is not defective, it should last a long 
time. The oxidation of the linseed oil will make the gasket 
tough, and if it is dusted with graphite every time the cylin- 
der head is removed it should be very durable. 

In using a gasket of asbestos and wire gauze having mate- 
rial on one side to make it adhere to the cylinder top, the 
opposite side being treated with graphite, there is no need 
of treating the gasket with linseed oil. A gasket of this 
sort is almost indestructible when care is exercised in tight- 
ening the holding nuts when the gasket is new. 



» -. 

> i 




4. ' 



1- ' 

. < 



■I - 

fi > 

■ ' 1 





!• There are occasions when it is necessary or advisable 
to make a careful study of the performance of a g^as engine 
tinder various conditions of working. For example, a 
manufacturer may be looking for defects, in order to apply 
the proper remedies; or, he may desire to possess a record, 
in order to offset possible complaints from purchasers 
regarding the non-fulfilment of the requirements of contracts. 
Also, a prospective buyer may want a test made for purposes 
of comparison with other engines, or of determining the make 
best suited to his needs; or, a user may have trouble with 
his gas engine and make a test to locate the difficulty, and, 
after repairs are made, make another test to ascertain 
whether the engine is in order. In cases like these, a prop- 
erly conducted test will bring out the good and the bad 
features of an engine as nothing else will. A thorough test 
will enable the engineer to determine whether the engine is 
wasting power, and, if so, to discover the cause; to ascertain 
whether the engine is correctly designed with regard to the 
sises and proportions of valves and passages, and whether 
the valves are properly set; and to locate many other faults 
that wotdd probably be overlooked and that continuous 
nmning would perhaps never reveal. 




While, however, a complete test is very often desirable, it 
is not always necessary. Perhaps all that may be desired 
will be the power that the engine can deliver to the 
machinery it is intended to drive, in which case a brake test 
only will be required. In order, however, that every detail 
may be understood, a test in its entirety will be described, so 
that whatever portions are required in actual practice may be 
used when wanted. 

2. In a gas-engine test, the following results are usually 
determined in order that the performance of the engine may 
be ascertained: (1) the brake horsepower; (2) the indicated 
horsepower; (3) the quantity of gas consumed per brake 
horsepower per hour; and (4) the lost energy due to heat 
carried away through the exhaust, by the jacket water, and 
by radiation from various parts of the engine. 

The Indicated horsepower (sometimes abbreviated to 
I. H. P.), so called because it is measured by means of an 
indicator, is the power applied to the piston of the engine 
by the explosion and expansion of the gases. 

The delivered horsepower (abbreviated to D. H. P.) 
is the name given to the power delivered by the engine to the 
belt or the machinery it is driving. The delivered horse- 
power is frequently called the brake horsepower (abbrevi- 
ated to B. H. P.), because it is measured by means of a 

From the measurements that must be taken to obtain the 
data just given, the performance of any engine can be 
readily analyzed. 


3. Prony Brake. — To make a test as just indicated, it is 
necessary to have an apparatus similar to that shown in 
Fig:. 1. which is a view of a form of absorption dynamometer 
known as the Prony brake and used to obtain the brake 
horsepower. The Prony brake consists of an iron strap a, to 
which are attached, with screws, a number of wooden friction 
blocks b. To each end of the strap is bolted a cast-iron 



block Cy so that the brake may be tightened by means of th 
bolt d and the nut e. Bolted to a are two boards /, /, formini 
the lever arm, or brake arm, and carrying at one end th 
steel knife edge g. This knife edge rests on a flat piece 
iron A, through which the pressure is transmitted to 
platform scale k by means of the stand /. 

4. Rope Brake. — A simpler form of brake, and oi 
suitable for light powers, is shown in Fig. 2. The bra^^^ 
proper consists of four or five ropes, as shown at r, or ^ 
piece of leather or canvas belting. The weight w is fasten ec/ 
to one end of the belt and a spring balance b to the other. 

The lower end of the 
balance is attached to 
a hook h screwed fast 
to the floor. If the 
pulley were perfectly 
free to turn, the read- 
ing on the balance 
would be equal to the 
weight of w\ that is, 
if the weight of w is 
50 pounds, the pointer 
on the balance' will be 
at 50. 

As the pulley is 
turned by the engine, the weight w is drawn upwards by 
the friction of the strap until the strap slips on the pulley. 
The total amount of pull will then be indicated by the 
decrease in the reading of the balance, or by the difference 
between the weight of w and the balance reading. Thus, 
if the balance reads 20 pounds, the pull on the belt will be 
w - 20, or 50-20 = 30 pounds. 

It is evident that, in either form of brake, the energy 
absorbed is converted into heat by overcoming the force of 
friction between the brake and the revolving wheel. In the 
simple forms of brake mentioned, it is a serious probletn to 
take care of the heat generated at high speeds, and for this 

Fig. 2 


on such brakes cannot be used on gfas engines except 
short periods of time, unless the heat is absorbed by 


I The Alden Dynamometer. — The Aid en dyna- 
neter is a type of brake that can be run continuously 

very little attention. Fig. 3 shows an elevation and part 
ion of such a dynamometer. It consists of the hub and 

casting a, the shaft d to which the casting is keyed, the 
;ing plates r, r, and the thin copper plates flf, d. The cop- 
plates are clamped at the outer edges between the two 
ling plates, and at the inner edges between rings and 
aubs of the housing plates. The copper plates are thus 

parallel and close to the disk a, in which are radial oil 
>ves for conducting oil all over the bearing surface 
reen the disk and the copper plates. Oil is fed to these 
>ves from the oil cups e, e, through the pipes /, / and the 
)assages g,gy in the housing hubs. The oil that works 
ray out around the hub to the recesses A, h is drained off 
ugh the pipes /, /. The copper plates and the housing 
5S form chambers /,/, which are filled with running water 
n the apparatus is in use. Water enters the bottom of 
e chambers through the pipe ^, the automatic regulating 
e /, and the pipe m. From the pipe tn, the water passes 
agh openings in the bottom casting n into the cham- 
j\j in the housing. The water fills the chambers, rises 

the space o, and flows out through the pipe p. The 
ir pressure in the chambers j\ j forces the copper plates 
nst the disk a, and sets up a friction that heats the cop- 
plates and tends to turn them with the disk. The heat 
rried off by the water, while the tendency of the copper 
js and housing to turn is balanced and weighed by the 
:ht g on the arm r. If the water pressure increases, the 
r goes up and partly closes the automatic valve /, thus 
)ring the equilibrium. 

^namometers of the Alden type have been built with 
I or four disks and large enough to absorb 2,000 to 
) horsepower at from 200 to 300 revolutions per minute. 







6. Tlie Dynamo as a Dynamometer. — One of the 

best means of absorbing work from a gas engine and con- 
verting it into heat is to use a dynamo, which for dynamome- 
ter purposes is preferably coupled to the shaft of the gas 
engine — that is, the dynamo and engine are direct-connected. 
The electricity delivered by the dynamo is absorbed by pass- 
ing it through a suitable resistance. The product of the 
readings of the ammeter and voltmeter placed in circuit 
gives the number of watts generated, which, divided by 746, 
will give the horsepower generated by the dynamo. To 
obtain the delivered, or brake, horsepower of the gas engine, 
divide this result by the efficiency of the dynamo, which has 
been previously determined at the load required. 

7. Tlie Gas-Eng^ine Indicator. — In making a test of 
a gas engine, the power exerted on the piston by the explo- 
sion and expansion of the charge is measured by means of 
an instrument known as an indicator, and shown at /, Fig. 1. 
The indicator used on gas engines is very similar to that 
used on ordinary steam engines; in fact, the same indicator 
is often used for both, with auxiliary attachments to adapt 
it to the gas engine. The piston of a gas-engine indicator 
should, however, be very light in order to give the best 

The purpose of the indicator is to determine the pressures 
in the engine cylinder at all points of the stroke, and to 
record these pressures in the form of a diagram on a paper 
or a card. In the case of the gas engine, the principal reason 
for obtaining an indicator diagram is to determine the cor- 
rect setting of the valves and the timing of ignition. The 
mean pressure may also be found, approximately, by the 
indicator diagram; but the shock of the explosion, the high 
speed of the engine, and the inertia of the indicator-pencil 
motion tend to reduce its accuracy for that purpose. 

8. Fig. 4 shows the general appearance of an indicator. 
The instrument consists essentially of a cylinder a contain- 
ing a piston and helical spring for measuring the pressure, 
the lever b for transmitting the motion of the piston to a 



pencil point f , and the drum d that carries the paper, or card, 
on which Ihe diagram of the motion is drawn. The card ( is 
held close to the drum by the clips shown at /, /, so that the 
pencil can easily trace the outline of the diagram. 

In Fig. 5 is shown a section of the same indicator. The 
piston, shown at g, must work in the cylinder as nearly 
frictionless as possible, the spring h being the only resislaoee 
to its upward motion. The spring is calibrated, that is. 
tested so as to determine the pressures required to move | 
the pencil c to various heights against Ihe resistance of the 
spring. The pressure, in pounds per square inch, thai ii 1 
required to compress the spring sufficiently to allow lli« || 
pencil to be moved up 1 inch is called the scale of the n 
sprInK- It is, therefore, possible to find the pressure in " 
the cylinder by the position of the pencil point when the I 
scale of the spring is known. By turning a small cock, shown 
attf. Fig. 1, in the pipe connectingthe indicator to the ensise 


cylinder, the gas pressure in the engine cylinder may, at 
pleasure, be admitted to or shut ofE from the indicator. 
When the gas pressure is admitted through the channel s, 
Fig. 5, it causes the piston ^ to rise. The helical spring A 

is compressed and resists the upward movement of the 
piston. The height to which the piston rises should then 
indicate correctly the pressure in the engine cylinder; and as 
this pressure rises and falls, the piston g must rise and fall 

9. To register the engine -cylinder pressure, a pencil 
might simply be attached to the end of the piston rod, and 
the point of the pencil made to press against a piece of 
paper. It is desirable, however, to restrict the maximum 
travel of the piston to about i inch, while the height of the 
diagram may advantageously be la to Ij inches. To give a 
long range to the pencil while keeping the travel of the 
piston short, the pencil is attached at c. Fig. 5, to the long 


end of the lever b. The fulcrum of the lever is at /, and the 
piston rod is connected to it at k^ through the link /. The 
pencil motion is thus much greater than the travel of 
the piston g\ for most indicators, it is four, five, or six times 
as great. The point c is made to move in a vertical straight 
line by the arrangement of the links 2, /, and g, 

10. The indicator, however, must not only register pres- 
sure, but must also register them in relation to the position 
of the piston. This registering is accomplished by means 
of the cylindrical drum shown at d^ Figs. 4 and 6. Th 
drum can be revolved on its axis m by pulling the cord 
that is coiled around it. When the pull is released, th 
spring Oy Fig. 5, turns the drum back to its original position 
If the cord n is attached to some part of the engine that ha 
a motion proportional to the motion of the piston, th 
motion of the drum must also be proportional to the motio 
of the piston. If the cord were attached directly to th 

piston or to some part having the same motion as the pistoi 3, 

the drum d would have to be so large that it would be cum^cn- 
bersome and the diagram correspondingly long and difficm^-Jt 
to handle. For these reasons, the drum is made small ar=:^d 
a device is employed for reducing the motion of the dru_ -m 
so as to give a convenient length of the diagram. Tb^is 
device, called a rediuing motiatiy will be explained later. 

The indicator shown in Figs. 4 and 5 can be used in taki^Kng 
diagrams from a steam engine or any other engine in whS. <h 
the pressure is not so great as in the gas engine. In orSler 
to do this, the piston g and its rod are unscrewed at p anc3 a 
piston that just fits the cylinder at p is attached. The a:i"ea 
of the cylinder at this point is just twice that of the piston. £; 
hence, only one-half as much pressure per square inch ^^i 
be required to produce the same pencil movement. 

11. To attach the indicator to the engine, a hole is drilled 
in the cylinder head into the clearance space of the engine 
and tapped for a i-inch pipe, shown at «, Fig. 1, with an 
elbow turned up and carrying a nipple and a valve o next to 
the indicator. The lower end s, Fig. 5, is inserted in the 


fitting attached to the valve and the connection r is tightened 
by means of the handle / shown dotted at u. When the indi- 
cator is to be used, a card or a piece of blank paper of con- 
venient size is placed around the drum, with the ends of the 
paper projecting from behind the clips through the space 
between them. The drum revolves with a motion propor- 
tional to the stroke of the engine, and the pencil moves up 
and down with a motion proportional to the pressure in the 
cylinder. Hence, by holding the pencil against the paper it 
draws a diagram recording these two quantities in such a 
way that they can be measured for every point of the stroke. 

12. . Manufacturers of indicators usually supply a special 
paper for use on the indicator, known as **metallic paper," 
which is made by coating ordinary paper with a special prep- 
aration that will turn black when rubbed with a brass wire. 
The indicator pencil may then be replaced by a piece, of 
ordinary brass spring wire, and the trouble of keeping a 
pencil sharp is obviated. Although the preparation of this 
paper is usually considered a secret, a coating of zinc oxide 
(zinc white, or Chinese white) will answer the same purpose. 
The zinc oxide is mixed with some gum solution or glue, and 
spread evenly over the surface of the paper. The paper is 
then allowed to dry, and is afterwards subjected to pressure 
for a day or two to remove the tendency to curl. The sur- 
face should be smooth and free from lumps or ridges, as 
these will cause unnecessary friction. Diagrams made on 
metallic paper are much more distinct than those made in 
the old way with a hard pencil. 

13. The indicator spring to be chosen depends entirely 
on the initial pressure of the exploded charge. The scale of 
the spring should be such as to give not over \\ inches verti- 
cal movement to the pencil for the highest pressure to be 
obtained on the cylinder. For instance, if the initial pres- 
sure is 175 pounds, a 100-pound or 120-pound spring should 
be chosen. The scale of the spring (100 pounds) indicates 
that the pencil will move 1 inch for each 100 pounds 
pressure per square inch on the piston. In general, it is 


advisable to select a spriag that will give a diagram betvees 
ll and I( inches high. A diagram less Chan 1^ inches in 
height is objectionable, for it is too small to show properly 
the valve setting; hence, in such cases, it is advisable to use 
a spring of lower scale. It may be found necessary to pro- 
vide the indicator with a safety stop, so that the piston wiD 
not rise too high and thus cause damage to the spring and 
other moving parts. 
The cylinder of the indicator /, Fig. 1, is connected to the 
compression space by i-indi 
gas pipe, as shown, a ping 
cock o being inserted between 
the engine and the indicator. 
A bunch of waste satniattd 
with water should be tied 
around the indicator at and 
kept wet constantly, in order 
to prevent damage to the in- 
dicator from overheating. 

]4. Reducing Motions. 

There are many devices- 
known as reducing mo- 
tlouB — for reducing the mo- 
lion of the engine piston to 
one suitable for the indicator 
drum. The reducing wheel r. 
Fig. 1, is perhaps the most 
*'"*^ convenient for general use. 

It is shown on a larger scale in Fig. 6; the cord a is attached 
to a rod on the piston, and the cord b is attached to the 
indicator drum. 

The other end of the cord a is attached to the large wheel 
and wound several times around it. As the cord a is pulled 
by the piston, it unwinds, turning the large wheel and the 
small wheel at the same time. The spindle of the small 
wheel has a screw thread of a pitch equal to the thickness 
of the cord, so that the arms of the cord guides, which Me 


held from turning about the spindle, are moved, with each 
revolution, along the spindle a distance equal to the thick- 
ness of the cord. Hence, the cords never wind over them- 
selves, but each cord is laid up in a continuous coil on the 
pulley as the other unwinds from its pulley. The pulleys 
being fastened together, the smaller turns with the larger; 
and, as the cord a unwinds one turn from the large pulley, 
the cord d unwinds from the indicator drum and winds one 
turn on the smaller pulley. Hence, the motion of the two 
cords is proportional to the circumferences or diameters of 
the two pulleys. 

The smaller pulley can be removed and replaced by one 
of several others of different sizes. The proportions of the 
two pulleys should be such that the length of the diagram 
will be between 22 and 82 inches. Thus, if the stroke of 
the engine is 12 inches, and the desired length of the 
diagram is 3 inches, the diameter of the larger pulley should 
be four times that of the smaller. 

15. The small sketch at the right of Fig. 1 illustrates the 
method of connecting the cord from the reducing wheel to 
the engine piston. A i-inch iron rod / is bent at right 
angles, as shown, and attached to the inside of the piston by 
two or three small machine screws. The end attached to 
the piston should, of course, be drawn out flat before the 
holes for the screws are drilled. A hook is made at m, to 
which the cord from the reducing wheel is to be attached. 
The wheel can be placed at any convenient point between 
the point m and the indicator. 

16. Reducing motions that employ gears are frequently 
used. Such a reducing motion, attached to an indicator, is 
shown in Fig. 7. This motion really consists of two wheels; 
on the larger one, shown at a, is wound the cord that is 
attached to the rod on the piston, and from the smaller 
one d runs the cord to the indicator drum. A spring in the 
horizontal case c acts on the pulley a through the bevel 
gears, resisting the pull of the piston on the string, on its 
outward stroke, and drawing in the string on the return 

IftS— 28 




stroke, thus always keeping the string tight. In the same 
way, the spring in the indicator drum d keeps the string 
tight between the drum and the pulley b. Frequently, the 
reducing wheel is attached 
directly to the body of the 
indicator, as shown in Fig. 7, 
thus avoiding the necessity 
of fastening it to the engine, ___ 
as shown in Fig. 1. Whei^^H 

the reducing wheel is at 

tached directly to the indi 
cator, the cord frotn th^^K 
wheel b. Fig. 7, to the ind^^E- 

cator drum d is short an ^ 

direct, making a >•- ^ 

with very little lost motio^^n. 
The wheel a is very pasi ~ -\ j 
detached from the mecha. -i- 
ism, and is one of seveir— aj 
different sizes furnished wm. tb 
P'o- 1 the apparatus, and used ^n 

engines of diSerent lengths of stroke. The cord guides- is 
arranged so that it can be turned to any position in its hc^n- 
zontal plane and fastened there, when it has only the vertSca/ 
motion necessary to lay the cord on the wheel uniformly. 

17. There should be some means arranged to stop tbe 
motion of the drum when not in use. This is easily done 
by dividing the cord from the indicator drum to the reduciaj: 
wheel, and connecting the two portions by means of the 
loop / and hook a. Fig. 8, 
The knots should be so . 
tied that they will not 
slip. The small piece 
of wood b makes a very 
neat arrangement about which to make the loop, as it will 
not slip and is easily united, and the length of cord is readily 
adjusted. In case the reducing wheel is connected to the 


pio. a 


indicator, as shown in Fig. 7, the hook is placed in the cord 
runnins^ from the reducing wheel to the rod on the piston. 

18. Gas Measor/Bment. — The gas that is supplied to 
the engine should be measured by a proving meter con- 
nected as shown at x. Fig. 1. Such a meter has a large dial 
and gives the number of cubic feet per hour from an obser- 
vation of 1 minute, as well as the total gas consumption over 
any period of time. The gas from the meter should pass to 
the engine through an india-rubber gas bag yy or some other 
form of pressure equalizer. In gasoline- or oil-engine tests, 
the fuel must be weighed. 

19. When it is necessary to measure the heat wastes 
and calculate the ratio each bears to the heat supplied, the 
heating value of the gas should be obtained. Quite fre- 
quently, the gas company has a record of the average heat- 
ing value of the gas it manufactures. If it has no such 
record, a sample of the gas should be sent to a laboratory to 
be properly tested for this value. This determination is 
absolutely essential to a complete test, or for a comparison 
of engines tested with different grades of gas. 

20. Cooling- Water Tanks. — In order to ascertain, the 
amount of heat carried off by the jacket water, it is necessary 
to know the weight of water that passes through the jacket 
and the rise of temperature caused by the heat of the engine. 
The weight of water may be measured in one of two ways: 
the water may be weighed directly, by means of a platform 
scale, using a tank or barrel set on the scale platform; or, if 
the scale is not convenient, the volume may be measured 
and the weight calculated. Since a certain volume of pure 
water at the same temperature always has the same weight, 
it is a simple matter to measure the water directly in pounds. 
For this purpose, the measuring tank ^, Fig. 1, is so con- 
structed that the depth of the water, in inches, gives its 
weight, in hundreds of pounds, when multiplied by 2. The 
tank is made of plank, and measures 37i in. X 37i in. inside 
dimensions. The height may be from 2 to 3 feet, as found 
most convenient. The stick s is marked off in inches or 



i inches as desired. This is used for measuring the depth 
of water in the tank. When the bottom of the tank is level, 
each 2 inches in depth indicates 100 pounds of water, and 
each a inch 25 pounds of water. If the stick is marked off 
in tenths of an inch, each tenth will indicate 5 pounds d 
water. These dimensions are computed for water at a 
temperature of 110° F, If a smaller tank or more accurale 
measurement is required, a tank 26i in. X 26i in. will pve. 
25 pounds for each inch on the stick, 100 pounds for eadi 
4 inches, and 5 pounds for each i inch. 

When the quantity of water used is small, or when wj 
accurate determinations are to be made, the water shonld 
be weighed. This can be done quite 
readily by using two receptacles and 
changing them at the moment of taldas 
the reading. For instance, if the read- 
ing is taken every 5 minutes, the strcain 
should be changed from one to the other, 
just as the signal is given. 

The temperature of the entering water 
is taken by a thermometer at I, and thai 
of the discharge at i'. The thermometers 
are not directly in contact with Ibe water, 
but are inserted in small cups contaicins 
oil. The temperature of the room is 
taken by the thermometer /,. 

21. Pyroinetop. — The temperature 

of the exhaust gases must be taken in 
order to determine the loss of beat by 
way of the exhaust pipe. As these tem- 
peratures are too high for the mercary 
thermometer, a form of temperature indi- 
cator known as a pyrometer is generally 
^"^- * used instead. A pyrometer is shown in 

Fig. 9. The stem 5 is composed of two tubes made from 
metals having different rates of expansion. The meUl^ 
generally used are copper and iron, the copper tube being 


tCCd inside the Iron tube, or vice versa. The entire s 
)m the nnt k should be subject to the temperature i 
sired 10 measure, 
nee the outside tube is 
ated first, the pointer 
tquently moves rap- 
s' forwards or back- 
irds around the dial. 
I soon as the stem is 
oronghly healed, the 

linter will indicate the temperature of the gases. A 
pyrometer is also shown at p, Fig. 1. 

32. KevoltitioD Counter. — The engineer 
should be provided with one of the three forms 
of revolution counters shown in Figs. 10, 11, 
and 12. The first is a continuous rounUr. the sec- 
ond a sfieed indicalor, and tlie third a tachometer. 
The arm a of the revolution counter, shown 
in Fig. 10. is attached to some reciprocating part 
of the engine. The number 
of revolutions per minute 
may be determined by means 
of a watch, and the number 
registered at the beginning 
and end of a minute noted. 
The difference between the 
second and the first reading 
will be the number of revolu- 
tions per minute. The read- 
ings of the counter may, instead, be noted 
at regular intervals (say of 10 minutes 
each), and the nHal number of revolutions 
registered during that time divided by the 
number of minutes; the result will be the 
number of revolutions per minute. 

Speed Indicator. — The speetl 

I In Pig. 11, registers the total number of 


revolutions. It is aati u 
follows: The hand]« h U 
held ID ibe hand, and the 
soft rubber point /> is thrust 
into tile center countersinlt 
on Ibe end of the crank- 
shaft; the dial d will Uiea 
register the number of rev- 
olutions. The best wb; to 
use this instrument is to 
have an assistant obserre 
the time. He should sive 
the signal "fio" at the be- 
giiining of the minttte, asd 
the signal "stop" just as the 
minute is up. First, set tli« 
instrument at zero, or care 
fully note the reading of ihe 
dial. Then, hold the pointy 
opposite the center, and »t 
the signal "go" ihrust/inw 
the center, holding it tight 
enough to prevent it from 
slipping. Note the onmber 
of revolutions of the dial 
and at the signal "stop" l")- 
mediately draw the indicalM 
away from ihe shaft. Aa 
the dial reads to 100, eni 
revolution of the dial will 
mean lOO revolutiDnsof ll* 
crank-shaft. Thus, if *« 
dial makes two turns and fl« 
pointer slops at 50, the bo"'' 
ber of revolutions lU 250- 

24. Thf Tucliometw- 


shown in Fig. 12, is an instrument for measuring the num- 
ber of revolutions of a shaft per minute. In principle, it is 
a small centrifugal machine, somewhat like the flyball engine 
governor. The handle a is held in the hand, and the pointer b 
is pressed into the center mark of the shaft. The pointer is 
removable and can be placed on the spindles c or </, as shown 
by the dotted lines, depending on the speed of the shaft. 
The spindle ^ is to be used for speeds less than 500 revolu- 
tions per minute; b, for speeds between 500 and 1,000 revolu- 
tions per minute; and </, for speeds between 1,000 and 2,000 
revolutions per minute. The pointed e is moved around the 
dial / by the movement of the weights, according to the speed 
at which they are driven. The instruments are usually made 
with three scales, and it is necessary to use the scale whose 
readings correspond to the spindle used. The axis of the 
instrument must be kept parallel with the shaft, and the 
spindle used must be in exact line with the axis of the shaft, or 
the vibration of the pointer will prevent accurate observation. 



25. The number of assistants required when making a 
gas-engine test depends entirely on the number and frequency 
of the readings to be taken. One man should watch the 
brake and keep the load constant by means of the nut €, 
Fig. 1; another should take indicator diagrams and note the 
speed; while a third should weigh or measure the water, 
note the temperatures, and read the meter. This la«it may 
sometimes be divided between two observers, making fnnr 
in all. In special cases, one man could take inOi'atnr 
diagrams and all readings; but such an arrangement jq not a 
good one, because a]] the readings should, if posqjhip, be 
taken at the same instant. With two ohsf'rvfT<?. fnOings 
should be taken every \h rr/inMf*-q. With thr"** n\ \n\\t 
observers, readings may be taken every 5 niinntHfl. 





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It is best to make several separate runs, each with a dif- 
ferent load on the brake. Twelve or more readings should 
be taken with each load, so that, if readings are taken every 
5 minutes, the run will last 1 hour, while with a 10-minute 
interval, it will last 2 hours. At least three runs should be 
made: one at full load, another at half load, and a third at no 
load. If the engine is a large one, several runs should be 
made at other loads, in order that the economy of the engine 
under these various conditions may be ascertained. It is 
also advisable to know the maximum load the engine is 
capable of carrying. The sensitiveness of the governor 
should be determined, where possible, by noting any change 
of speed when passing suddenly from full load to no load. 
The person in charge should be provided with a whistle. 
Thirty seconds before the time for taking the readings, he 
should blow two blasts on the whistle, when every observer 
should at once go to his post. At the moment for taking 
the readings, one blast should be blown, and all readings 
must, as far as possible, commence at the signal. No 
looker-on should be allowed to interfere with the observers, 
and no observer should rely on any one else, particularly an 
outsider, to take or record the observations allotted to him. 

Before beginning a trial of any kind, the one in charge 
should see that a sheet is already prepared for recording the 
data observed while the trial is in progress. This sheet — 
called the log — should be ruled in horizontal lines and ver- 
tical columns, and each column should be headed with an 
explanatory phrase or note, showing what particular record 
is to be placed in that column. Keeping notes on loose 
sheets of paper is bad practice. The accompanying log of 
test is a very convenient form for the purpose. There 
should be lines enough for recording at least fifteen sets of 
observations. Only such observations as are taken during 
the test, together with the individual results from each 
reading, should be entered on the log. 



26. After the first test is made and the data are obtained, 
the report should be written. A convenient form for the 
report is shown on the next pas:e. 

The space before the words gas engine should be filled in 
with the maker's name, and made by should be followed by 
the name of the person or eng^ineering firm that made the 
test and is responsible for the accuracy of the results. The 
next line should contain the name of the locality where 
the test was made, followed by the date. 

The report should be made out in duplicate, one copy being 
kept by the party that makes the test, and the other \xxag 
S^ven to the party for whom the test is made. 

27. Clearance. — The first three dimensions in the pre- 
ceding^ report blank are obtained by actual measurement, and 
need no explanation. The piston displacement is the 
product of the area and the stroke of the piston, and is usn- 
ally expressed in cubic feet. The clearance is measured 
most readily in the following manner: Place the crank on 
the inner dead center, and close every opening but one, 
which should be on top. Then weigh a bucketful of cold 
water, and pour it through a funnel into the compression 
space, taking care that none is spilled and that the compres- 
sion space is just full and no more. Weigh the water that 
remains in the bucket, and subtract this amount from the 
first weight. Divide the remainder by 62.5, and the result 
will be the clearance, in cubic feet. 

Let C = clearance, in cubic feet; 

JF= first weight, in pounds; 
w = second weight, in pounds. 

^''"- ^.= -if 

In the larger engines, more than one bucket of water niat 
be required, and W should then be taken as the sun: of ±e 
weights of the full buckets, and -c the sum of the weights cf 
the buckets from which the water has been poured. 


.Gas Engifu 


iiONS OF Engine 

piston In. 

on Sq. in. 

troke Ft. 

acement . . Cu. ft. 

■ • . • • • .V'll. It . 


al Hr. 

X • • • • • • ^^ U • LL« 

r Cu*. ft. 

o air 

r per hour . . . Lb. 
r temperature, inlet 
r temperature, outlet 
r temperature, 

.... Degrees, F. 
per minute. Average 

per hour 

per minute. Average 

per hour 

'e exhaust, 

.... Degrees, F. 
eroom . Degrees, F. 
5ver arm .... Ft. 

average . . . .Lb. 
t of cubic foot . Lb. 

Air — weight of cubic foot . Lb. 
Mixture — weight of cubic 

foot Lb. 

Specific heat, gas 

Specific heat, air 

Specific heat, mixture 

Heat value cu. ft. gas . B. T. U. 

Work— ft.-lb. per min . Average 
Work— ft. -lb 1 per hour Average 

B. H. P Average 

Indicated M. E. P. . . Average 
Indicated H. P. ... Average 

Gas per I. H. P Cu. ft. 

Gas per B. H. P Cu. ft. 

Mech. eff. B. H. P. -i- I. H. P. 
Friction loss I. H. P. - B. H. P. 

Heat Per Hour 
Supplied by gas . . . B. T. U. 
Absorbed by jacket wa- 
ter B. T. U. 

Exhausted B. T. U. 

Absorbed in work . . B. T. U. 
Radiation B. T. U. 

I Thermal efficiency . . Per cent. 
i B. T. U. per I. H. P 


The percentage of clearance is found by dividins: the clear- 
ance by the piston displacement. 

Example. — The diameter of an engine cylinder is 10 inches, and the 
length of the stroke is 12 inches. A bucket of water is found to weigh 
21 pounds, and after filling the compression space the bucket and 
remaining water weigh 9.5 pounds. What is: (a) the piston displace- 
ment, in cubic feet? {b) the clearance, in cubic feet? {c) the 
percentage of clearance? 

Solution. — (a) The piston displacement is 

area X stroke = .7854 X 10* X 12 = 942.48 cu. In. 
= 942.48 -^ 1,728 = .5454+ cu. ft. Ans. 
{b) Substituting in the formula, 

^ W^w 21-9.5 ,o. ,^ . 
^ ' -62:6- = -62X- = -^^ ^^- ^*- ^^^- 
(c) Dividing the clearance by the piston displacement, the pe 
centage of clearance is 

.184 -s- .5454 = .337 or 33.7 per cent. Ans. 

28. Volume of Air Used. — The air used per hour m ay 
be found, roughly, by deducting the amount of gas used 
per explosion from the piston displacement, and multiplying' 
this quantity by the number of explosions per hour. 
Let " Z' = piston displacement, in cubic feet; 
G = cubic feet of gas per explosion; 
E = number of explosions per hour; 
A = cubic feet of air used per hour. 
Then, A^= {P - G) E 

Example. — A gas engine has a piston displacement of .5 cubic foot, 
and the amount of gas used per explosion is .06 cubic foot; when 
exploding 5,000 times per hour, how many cubic feet of air is used 
per hour? 

Solution. — ^Substituting in the formula, 
A = {P - G) E = {.b - .05) 5.000 = .46 X 6,000 = 2,250 cu. ft. Ans. 

While this method for finding the^volume of air taken into 
the engine is frequently used, it is better to measure the air 
by means of a meter. The ratio of the gas to the air is the 
ratio of the quantity of gas supplied per hour to the quantity 
of air used in the same time. Thus, if 50 cubic feet of gas 
is used per hour, and 400 cubic feet of air is used in the satne 
time, the ratio of gas to air will be 50 : 400, or 1 : 8. 


'. Ueasurement of Oas Presanre. — Since the pres- 
dealt with in gas supply and distribution are quite 
, it is the custom to use a unit of measurement of the 
ure smaller than the pound per square inch. The 
Tsally adopted unit is the pressure per square inch 
ed at its base by a column of water 1 inch high, 
» is .03617 pound. For the sake of brevity and 
:nience, the pressure is not reduced to pounds, but 
:pressed by simply stating the height of the water 
m, in inches, that the pressure will balance. Thus, if 
is a pressure in a gas main sufBcient to 
ce a column of water 4i inches high, the y^^y 
ure is said to equal, or to be, H inches of ff \ 

e pressure of gas is measured by means 
e same instruments used for air and other 
>us fluids. The construction of the instru- 
s, however, is varied somewhat for con- 
nce in handling. 

e most common form of gas-pressure gauge 
jwQ in Fig. 13, and is variously known as a 
^r gange, a siphon gauge, or a U gauge. 
ube a is made of metal, and is provided with 
:ket d that will screw on any ordinary gas 
e in the place of a burner. The tubes i 

are made of glass, and are filled with water 
■ the zero of the scale. The scale is grad- piq. u 
. in inches and convenient fractions of an 

The tube £ is open to the air at the toi». When the 
ure is admitted to the tube a, the water will sink in the 
6 and will rise in c. The difference in the height of 
ater in the two tubes, measured in inches, is the raeas- 
f the pressure exerted in inches of water. The depres- 
below zero in b should be added to the rise above zero 

The fall in one tube will not exactly equal the rise in 
ther, unless the tubes are of exactly equal bore. The 
ure of the gas is recorded in the log of the test in 
s of water. 


30. Gas Consumption. — Comparisons with other 
eng^ines should always be made as nearly as possible 
under the same conditions. A gas engine will lose more 
heat by radiation in a cold room than in a hot one, and a 
considerable diflEerence in gas consumption will be noted 
when working with cold or with hot jacket water. 

For the comparison of engines working with different kinds 
of gas, the heat value of the gas used, in British thermal 
units, is a much better basis than the gas consumption; for 
a gas engine that will need 20 cubic feet of city gas to 
develop 1 horsepower may require 80 cubic feet of producer 
gas per horsepower; or the same engine may develop 
1 horsepower on 10 or 12 cubic feet of natural gas. If, 
however, the gas for the several engines to be tested should 
be taken from the same source, a comparison of the gas 
consumption per horsepower will be sufficient. 

31. Temperatures. — A double purpose is served by 
taking the temperature of the water as it enters and as it 
leaves the jacket. The first is that the operator is enabled 
to regulate the temperature during- the trial; and the second, 
that the water acts as a factor in the measurement of the 
loss of heat through the jacket. This loss of heat is, of 
course, not altogether the fault of the engine itself, for much 
depends on the way the flow of water is controlled. The 
best makers advise the use of a circulating tank, in which 
the water soon reaches the boiling point, and which reduces 
to a minimum the amount of heat carried away. 

The determination of the exhaust temperature is not so 
important in a partial test as the determination of the jacket- 
water temperature, but it serves as a check on the indicator 

The temperature of the room should be subtracted from 
the exhaust temperature in calculating the loss through the 
exhaust; for the temperature of the gas and air entering the 
engine cylinder is approximately the same as that of the room, 
and the heat thus carried into the engine must be deducted 
from the heat in the exhaust, in order to determine the 


amount of heat due to combustion that is lost in the 

The temperature of the room will give some idea as to the 
loss due to radiation from the engine. An exceedingly high 
temperature indicates a large amount of radiation; while a 
normal temperature indicates but slight radiation loss. The 
specific heats of the gas, the air, and the mixture will be 
treated under Heat Losses, while the thermal and mechanical 
efficiencies will be taken up in connection with the subject of 

32. The readings having all been obtained, it is possible 
to trace the heat wastes from calculated results and to dis- 
cover the cause of any abnormal loss. Nothing but a 
proper interpretation of the indicator diagram will show 
faults in valves or igniters. The wastes having been 
determined in a general way, the next step to consider is 
the calculation of the results from the data obtained. It is 
best to have a competent assistant to work up the results 
independently, the separate computations acting as a check 
on each other. If the two results thus obtained agree, they 
may generally be considered correct. 


83. To determine the brake, or delivered, horsepower, 
three things must be known: (1) the pressure exerted at 
the end of the brake arm; (2) the length of the arm; and 
(3) the number of revolutions made by the crank-shaft in 
1 minute. The work is dgne on the brake at the rim of the 
wheel to which the brake is attached. It is not convenient 
to weigh the resistance of the work at the rim of the wheel; 
hence, this is done at the end of the brake arm — a distance / 
from the center of the shaft. The product of the resistance 


at the rim of the wheel and the radius of the wheel equals 
i times the pressure weighed. The result is that the work 
may be considered as being absorbed at a distance / from 
the center of the shaft — that is, at the end of the brake arm. 


If the brake arm were permitted to move with the pulley 
Against a pressure equal to that exerted on the scales, it 
would be exerting: that thrust throus^h a distance, per minute, 
equal to the distance the end of the arm would traverse in 
that time. Now, it is evident that in one revolution the arm 
will describe a complete circumference, the lens:th of which 
will be equal to 2 ;r /, where / is the length of the lever 
in feet; and the total distance traversed in 1 minute will 
equal to 2:: In, where n is the number of revolutions mad( 
by the crank-shaft in 1 minute. This total distance traversec^^ 
multiplied by the pressure p gives the number of foot-poun< 
of work done in 1 minute; and, since the capacity to ^^ 
33,000 foot-pounds of work per minute is 1 horsepower, tt:::::::^^ 
formula for the brake horsepower is 

B. H. P. = 1^^ (1) 


Example. — What is the brake horsepower of a gas engine when -^^ 
brake arm is 3 feet long, the pressure on the scales 25 pounds, and the 
revolutions per minute 200? 

Solution. — Here, / = 25 pounds, / = 3, and n = 200; hence, 
3 jj p _ 2_><3J41^^><3X200 ^ 2 ggg J, p ^^ 

Since, during any trial in which the same brake is used 

throughout, the brake arm does not change, the factor 

-— V-— is the same for all readings. Ascertain this once 

33,000 ^ 

for all, and call it c. Then simply multiply c by pn io 

each separate determination. Suppose, for example, th^ 
/ = 6 feet; then, 

c = -J^ = .001142 (2) 


and B. U,F, = cfin = .001142 pn (3) 

It is generally advisable to keep the pressure p cons 

during a single run, in which case a new constant ca 

computed for each particular run, which will inclu^ 

Calling this new constant C then 



brake arm will be - 

= 18i laches. 

In the ordinary form of Prony brake, the leng^th of the 
brake arm / is the distance from the center of the crank' 
shaft to the point where the knife edge exerts its pressure 

on the scale. This distance is denoted by L in Fig. 1. 

The lever arm of the strap or rope brake, illustrated in 
Fig. 2, is the distance from the center of the shaft to the 
center of the strap or rope. For example, if the diameter 
of the pulley is 36 inches and the belt is i inch thick, the 


For Prony brakes, it is necessary to take into account the 
weight of the unbalanced arm. because in high-speed tests a 
very small weight may represent a large horsepower. lo 
order to do this, the brake is loosened from the flywheel or 
pulley, and the arm is allowed to rest on the platform scale 
as when making the test. The pressure that the unbalanced 
portion of the arm exerts is then weighed, and this weight 
must be subtracted from the pressure on the scale when 
making a brake test. 

34. The Pianlmeter. — To compute the indicated horse- 
power from the indicator diagram, the average, or mean, 
height of the diagram must be found. The easiest and most 
accurate way to do this is to get the area of the diagram by 
means of a plan I meter, and to divide this area by the 

length of the diagram. A planimeter suitable for this pur- 
pose is shown in Fig. 14. It consists of two bars a, b with a 
hinged joint c and a roller d. At the end of the bar i is a 
weighted point e, which is pressed into the paper just enough 
to fix it in one position; the bar b then moves about the 
tat*- - 20 


joint e when the planimeter is in use. The point / on tl^^^' 
arm a is the tracing point, which is moved over the outlii 
of the diag^ram. The roller d has on one edge a flangt 
which should roll on a smooth surface; and behind the flanc[* 
are graduations, giving readings in square inches and tenth 
of a square inch. By means of a vernier g^ the graduation: 
on the roller may be read to hundredths of a square inc) 
There are a number of types of planimeters in use, difiEerinj 
in construction but operating in the same manner. Th 
mode of reading may differ considerably, but complel 
instructions are always furnished with each instrument. 

The planimeter should be used on a smooth level surfac- ^r( 
a drawing board covered with a heavy well-sized paper 
with bristol board answers very well. The indicator can 
is fastened to the board, and the planimeter is set in a1 
the position shown in the figure. The starting point 
marked with the tracing point /, and the recording rol^ier 
adjusted to zero. The outline of the diagram is then ca^re- 
fully traced with the point /, being sure to stop exactly^ on 
the starting point. The reading taken will be the aresi 0/ 
the diagram, in square inches. 

35. The area is read from the recording wheel and ver- 
nier as follows: The circumference of the wheel is divided 
into ten equal spaces by long lines that are consecutively 
numbered from to 9. Each of these spaces represents an 
area of 1 square inch, and is subdivided into ten equal spaces, 
each of which represents an area of .1 square inch. Starting 
with the zero line of the wheel opposite the zero line of the 
vernier, and moving the tracing point once around the dia- 
gram, the zero of the vernier will be opposite some point oj 
the wheel; if it happens to be directly opposite one of tb 
division lines on the wheel, that line gives the exact area 
tenths of a square inch. The zero of the vernier, howev 
will probably be between two of the division lines on 
wheel, in which case write down the inches and tenths 
are to the left of the vernier zero, and from the vernier 
the nearest hundredth of a square inch as follows: Fin 




I 4 



line of the vernier that is exactly opposite one of the lines 
on the wheel. The number of spaces on the vernier between 
the vernier zero and this line is the number of hundredths 
of a square inch to be added to the 
inches and tenths read from the wheel. 
For example, in Fig. 15, the of the 
vernier lies between the lines on the 
wheel representing 4.7 and 4.8 square 
inches, respectively, showing that the 
area is something more than 4.7 square — 
inches. Looking along the vernier, it 
is seen that there are three spaces be- 
tween the vernier zero and the line of 
the vernier that coincides with one of the lines on the wheel; 
this shows that .03 square inch is to be added to the 4.7 square 
inches read from the wheel, making the area 4.73 square 
inches, to the nearest hundredth of a square inch. 

36. While the form of planimeter shown in Fig. 14 is 
very convenient, a much simpler and less expensive instru- 
ment, called the hatchet planimeter, shown in Fig. 16, 
may be used for measuring the areas of indicator diagrams. 

Pio. 15 

Pio. 16 

This simple instrument, if accurately made and used with 
proper care, will give very satisfactory results. It is made 
of i-inch steel rod bent at both ends, as shown. The end a 
is sharpened for a tracing point, and the other, b, is flattened 
like a hatchet. The distance between the tracing point and 




the point at which the curved hatchet end b touches the 
paper should be at least twice the length of the indicator 
diagram; 10 inches is a desirable length for ordinary use. 

r^%trw^eir=^#==;rTfcS?>T»^^^y^*^ ^ 




^J _•- - - • * " • 

i # 3 * 

Fio. 17 

The method of using the hatchet planimeter is shown in 
Fig. 17. The indicator card a is fastened to a drawing 
board over a piece of smooth heavy paper or bristol board b 
that is of sufficient size to furnish the surface for the records 



made by the hatchet. The center of gravity c of the dia- 
S:ram must be located. This may be done approximately by 
inspection, or it may be found quite accurately by cutting: 
out the diasfram and balancing it on the point of a pin. 
Draw a line A B through the center of gravity parallel to 
the atmospheric line /, extending it on the bristol board 
beyond the card a. With ^ as a center and the length of the 
planimeter as a radius, describe an arc d on the paper b. 
Then place the planimeter approximately at right angles to 
the atmospheric line /, and, with the tracing point at c^ 
make the mark 1 on the arc d with the hatchet end; proceed 
with the tracing point from c to g, and thence over the outline 
of the* diagram, moving clockwise and back to c. During 
this movement, the hatchet end is free to move lengthwise 
on the paper h as the tracing point moves around the dia- 
S^ram. It is best to hold the instrument, just above the 
tracing point, between the thumb and forefinger, keeping the 
arm of the tracing point vertical and preventing the hatchet 
from slipping sidewise. The hatchet will stop at some 
point 2 on the arc d. Next revolve the card 180° about the 
point ^, as shown by the dotted diagram, until the horizontal 
line A B coincides with the extensions A' B' on the paper b. 

With the hatchet at 2, move the tracing point from c to / 
and around the diagram in a counter-clockwise direction, 
returning to c. The hatchet will stop at some point 3 near 1. 
Locate the mid-position 4 between 1 and 3 and measure the 
distance from 4 to 2, using an accurately graduated scale. 
A scale graduated to fiftieths or hundredths of an inch is 
most convenient. The area of the diagram, in square inches, 
will then equal the distance 4-2 multiplied by the length of 
the planimeter. 

In order that the measurement may be accurate, it is 
necessary that the tracing point and the arc forming the 
edge of the hatchet lie in the same plane, and that the dis- 
tance between the points / and 2 and the length of the 
planimeter are correctly measured. It is best to locate the 
actual center of gravity of the diagram, although a small error 
in this respect will not cause serious inaccuracy, provided the 




planimeter is set approximately at right ang:les to the 
pheric line when starting. 

The alinement of the hatchet with the point may be tested! 
by drawing a straight line on a horizontal drawing bond, I 
and then placing both tracing point and hatchet onthelae 
and moving the tracing point along it. If the plane of fix 
hatchet is true, the hatchet will follow the line; if not, itiil 
run to one side or the other. 

37. Mean Effective Pressure, — To determine Ae 
mean effective pressure from the indicator diagram, the fint 
thing to do is to find the length of the diag:Tam. To do tUs, 
draw two lines just touching the diagram at its extreme 

Fio. 18 

limits, and perpendicular to the atmospheric line, as illus- 
trated in Fig. 18. The length will be the horizontal dis- 
tance L between these two lines. The area of the diagram 
divided by the length gives the mean height, or mean ordi- 
nate. This mean ordinate multiplied by the scale of the 
indicator spring gives the mean effective pressure, or M. E. P. 
Let a = area of diagram, in square inches; 
L = length of diagram, in inches; 
s = scale of spring. 


M. E. P. = ^ 

Example. — The area of a certain indicator diagram is 2.17 square 
inches, the length is 2.9 inches, and the scale of the indicator spring 
is 120; what is the mean effective pressure? 





as 2.17X120 

M. E. P. = -^ = -^^ 

=s 89.8 lb. per sq. in., nearly. Ans. 

38. Where a planimeter is not available, the following 
method of finding: the mean effective pressure is fairly rapid 
and accurate: Draw a tangent to each end of the diagram 
perpendicular to the atmospheric line. Then, accurately 
divide the horizontal distance between the tangents into ten 
or more equal parts (ten or twenty parts are the most con- 
venient, but any other number may be used). Indicate, by 





Fio. 19 

a dot on the card, the center of each division, and through 
these dots draw lines parallel to the tangents from the upper 
line to the lower line of the card. On a strip of paper, mark 
off successively, and with care, the lengths of these lines, 
the total length thus representing the sum of all the lines. 
Measure this total length, divide by the number of measure- 
ments made, and multiply the quotient by the scale of the 
spring; the result will be the mean effective pressure. 

A convenient method of dividing the length of the diagram 
ABt Fig. 19 {a), into the desired number of parts is to draw 
the line ^Z, at a small angle to ^^, and then lay off any 
convenient length, as A C, the required number of times 




successively, along: A Z, In this case, AB is to be divided 
into ten equal parts, hence ^ C is laid off ten times successively 
from A to Z. Next connect B to Z, and draw short lines from 
the points C, Z?, -£*, etc., parallel to B Z and intersecting A B. 
These points of intersection will divide the line A B into the 
same number of equal parts into which the line AZis divided. 
A more convenient method is to locate the middle points 
of the divisions A C, CD, D E, etc. on A Z, and draw lines^ 
from these middle points parallel to BZ intersecting A B ii^ 
the middle points of its equal divisions. To find the meari. 
effective pressure, erect perpendiculars at the middle points 
of these divisions as shown at ab, cd, ef, etc. Find the 
average length of these lines by laying them off in succes- 
sion on a piece of paper, as shown at a'^', c'^d', e! i\ etc. 
to //', Fig. 19 (A). Measure the length from a' to /', and 
divide it by the number of parts into which the diagram was 
divided. Multiply the quotient by the scale of the spring, 
and the result will be the mean effective pressure, in pounds 
per square inch. 

39. The experimenter will frequently encounter an engine 
making a diagram similar to that shown in Fig. 20, with a 
loop enclosing the atmospheric line. In such a case, the area 

Fio. 20 

of the small loop should be subtracted from that of the larger 
diagram, before calculating the mean ordinate. The lower 
line of this loop represents the pressure in the cylinder as the 
charge is drawn into the engine, and the upper line represents 


the pressure as the exhaust gases are passing: out. Hence» 
the area of the loop represents the work lost in these two 

40. Horsepower Formula. — To compute the indicated 
horsepower, the following: formula is used: 

I. H. P. = $^ 

in which / = mean efiEective pressure, in pounds per square 

/ = length of piston stroke, in feet; 
a = area of piston, in square inches; 
n = number of explosions per minute. 
As in the calculations for the brake horsepower, the dimen- 
sions / and a being the same for all calculations, that portion 
of the formula which includes these terms may be computed 

Example. — In testing a gas engine, it is found that the mean 
effective pressure is 75 pounds; the stroke of the piston, 6 inches; 
the area of the piston, 16 square inches; and number of explosions 
per minute, 70. What is the indicated horsepower? 

Solution. — / = 76 lb. per sq. in., / = 6 in. = .5 ft., a = 16 sq. 
in., and n =» 70. Then, 

^- ^- P- ' ^^^'sSflOO^^^ " ***** ' ^-^^"^ "• ^' ^°^- 

41. It is often desired to calculate, approximately, the 
maximum horsepower that an engine is or should be capable 
of developing, without going to the trouble of taking indi- 
cator diagrams. In such a case, the following formula may 
be used for four-cycle engines: 

I.H.P. =>^^^^ (1) 


in which I. H. P. = indicated horsepower; 

d — diameter of piston, in inches; 

/ =s mean effective pressure, in pounds per 

square inch; 

r »= number of revolutions per minute; 

n = number of cylinders; 

/ = length of stroke, in inches. 




This formula differs from the one gfiven in Art. 40, anii 
as it gives only approximate results, it should not be nsei. 
where accuracy is required. 

If the engine is of the two-cycle type, the rigrht-hand mem- 
ber of formula 1 is multiplied by 2 and the formula becomes 

I.H.P. = ^;^^ (2) 

600,000 ' 

Example. — The diameter of the cylinder of a sing^le-cylinder foo^ 
cycle engine is 6 inches, and the length of the stroke S& 8 incbei 
If operated with gasoline at a mean effective pressure of 75 poaadi 
per square inch, it makes 180 revolutions per minute; what is tbe 
probable indicated horsepower? 

Solution.— In this case, ^ = 6X6 = 36, / = 75, / = 8, r = ia 
and n = 1. Hence, substituting in formula 1 g^ves 

T w T> 36 X 75 X 8 X 180 X 1 o oq w r> , a 

I. H. P. = 1 000 000 ~ » °®*^Jy- -Ans- 

Table I gives the most suitable compression in absolnte 
pressure and the mean effective pressures for engfines usin^ 
the ordinary gas-engine fuels. 




Compression, in 

Pounds per Square Inch 


Mean Effective Pressure 
in Pounds 
per Square Inch 

Kerosene .... 

45 to 70 

40 to 80 


65 to 95 

60 to 100 

City gas 

45 to 90 

45 to 95 

Natural gas . . . 

115 to 135 

70 to 90 

Producer g^as . . 

90 to 150 

60 to 100 

Blast-furnace gas 

140 to 180 

50 to 80 

42. The amount of gas used per indicated horsepower 
per hour is found by dividing the gas consumed per hour by 
the indicated horsepower. The gas per brake horsepower 
is found, in a similar manner, by dividing the hourly con- 
sumption by the brake horsepower. The loss due to friction 
is the difference between the indicated horsepower and the 


farake horsepower. Thus, I. H. P. — B. H. P. ■- the friction 
loss, in horsepower. 

The heat supplied by the gas per hour is the heat value of 
1 cubic foot of the gas in British thermal units multiplied by 
the number of cubic feet used in 1 hour; for example, if the 
heat value is 650 British thermal units per cubic foot and the 
hourly gas consumption is 50 cubic feet, the heat supplied to 
the engine per hour is 650 X 50 = 32,500 British thermal units. 


43. The following computations of heat wastes are 
absolutely necessary only when making a complete heat 
analysis of the engine. It is always best that such a test be 
made under the direct supervision of a competent engineer. 
The following outline for such an analysis is given for the 
purpose of explaining the process involved sufficiently to 
enable one to determine whether such a test is desirable in 
any specific case. 

44. The heat absorbed by the water-jacket is equal to 
the weight of water passed through the jacket multiplied by 
the temperature range; or, in other words, it is the difference 
between the temperature of the water when it enters the 
water-jacket and that of the water when it leaves the jacket. 
For instance, if the temperature of the entering water is 50® 
and that of escaping water is 180®, the temperature range is 
180® - 50® = 130®. Then, if the weight of the water passing 
through the jacket in 1 hour is 100 pounds, the heat carried 
away is 100 X 130 = 13,000 British thermal units. 

46. To determine the heat carried away by the exhaust 
gases, the specific heat, as well as the weight of the gas, in 
pounds per cubic foot, must be known. City gas at atmos- 
pheric temperature and pressure weighs, approximately, 
.078 pound per cubic foot. The specific heat of air is, 
approximately, .238 at constant pressure; that of city gas 
may usually, without serious error, be taken as .22. For 
accurate observations, the specific heat must be ascertained 
for the particular kind of gas used. These quantities being 


known, the weis^ht and the specific heat of the xnizture, or 
chars:e. can be calculated quite readily. The formula for 
the heat H per hour carried away by exhaust is 

/^ = 5a^^(/» — /,) 
in which s = specific heat of mixture; 

w = weig^ht of 1 cubic foot of mixture; in pounds; 
q = quantity of mixture exhausted per hour, in 

cubic feet; 
/. = temperature of exhaust ascertained by pyrom- 

/, = temperature of room. 
The volume of the mixture passing through the exhaust 
is found, approximately, by multiplying the volume displaced 
by the piston by the number of explosions. 

Example. — The weight of a cubic foot of the exhaust gases of a 
certain engine is found to be .068 pound per cubic foot; the specific 
heat of the mixture is .23; and the number of cubic feet of gas 
exhausted per hour is 90. If the temperature of the room is 80° F., 
what is the quantity of heat carried away by the exhaust when the 
temperature shown by the pyrometer is 350® F.? 

SoLmoN.— Substituting in the formula, H = 5wq{tx ^ t^^s ^ .23, 
a- = .C^v<. V = 30. /, = a30°, and /, = S0=. 

H = •::> \ A>>S \ 30 X v350 - S0:> = 126.68 B. T. U. Ans. 

4G. The heat absorbed in work is that delivered to the 
piston in inuicared horsepower. The mechanical equivalent 
of a British thermal unit is 77S foot-pounds; hence, as a 
horseivnver is the capacity to do 33,000 foot-pounds of work 
per :r.i::u:e, the fomrjla for transforming the indicated horse- 
power British thermal units per hour becomes 

,. ^ ,. I. H. P. X 33.000 X 60 

. r B. T. U. per hour^ = 2..>45 I. H. P. 

KxAMiLr — '♦ > :::e _uj.-:::yof hejLt absorbed in work per bozr 
:t :--.r r. -v.v;.i:c.: hcrs^r^cwer of which is 25? 

-• ; — J — 

- ^ • = : -4^- V *:^ = 6:^.625. A=$ 

» * « »• % 

emams alter suDtracting the 
■-. * redoing three calculations fr-:n: 




The determination of the indicated horsepower is 
either the only nor the most important use of the indicator 
i^gram; it also serves to show what is taking: place in the 
ylinder durins; the time that the diagram is being produced. 
^n engineer thoroughly familiar with the operation of the 

Fig. 21 

^as engine can usually locate a defect much more quickly 
from an examination of its diagram than from a tedious 
examination of the engine itself. 

The diagrams shown in Fig. 21 are, with one exception, 
copies of actual diagrams. Diagram A was taken from a 


Homsby-Akroyd oil eng:ine using: ordinary kerosene oiL 
The cycle is the same as that of the Otto g^as eng^ine, and the 
diagram is shown as an excellent example of what a g:ood gas- 
engine diagram should be. That there is very little resist- 
ance in the admission and exhaust passages is shown by the 
curved lines that lie close to and just above and below the 
atmospheric line xy. These show but little rise or fall of 
pressure. The curve above the atmospheric line, if high, 
would show resistance in the exhaust passages, and that 
below the atmospheric line would show resistance in either 
the gas passages, the air passages, or both. Compression 
begins at a, and the pressure of the charge is gradually 
increased until, just before the piston reaches the end of 
the compression stroke, the charge is ignited at b. The 
point b of ignition is shown by the sudden change in the 
direction of the compression line. The advantag:e gained 
by ignition taking place just before the completion of the 
compression stroke is shown by the line ec. This line is at 
right angles to xy^ proving conclusively that the charge was 
fully inflamed before the piston started on its forward stroke. 
This is as it should be; that is, the point of maximum pres- 
sure is at the beginning of the stroke, just before the piston 
starts forwards. 

The ragged appearance of the diagram at the beginning of 
the forward stroke is not due to any fault of the engine, but 
to the vibration of the indicator spring, caused by the rapid 
rise of pressure from e to c. The curve would otherwise be 
quite regular from c to d, as shown by the dotted lines. The 
fall from f to t/ is gradual, and the form of the diagram after 
release at d shows a quick-opening exhaust valve and very 
little resistance in the exhaust passages. 

48, An example of late ignition is shown in diagram B. 
lo^nition takes place at a just after the crank has passed the 
center. The result is that the initial pressure is much below 
what it should be, and the maximum pressure occurs too 
late in the stroke. The effect of this derangement is shown 
more distinctly in diagram C, where ignition takes place 


much later in the stroke. The dotted line shows the shape 
of the diagram obtained when ignition takes place at the 
proper point, the area abc being the measure of the power 
lost. The areas are indicated by the figures on the diagram, 
.52 being the area, in square inches, of abcy and 1.10 that 
of the actual diagram. This shows that very nearly one- 
third of the available power has been lost through faulty 

49. Bad as late ignition is, too early firing is no better, 
because it checks the speed of the engine and causes an 
injurious pounding. It may even cause a reversal of the 
engine at low speeds and light loads. A diagram illustra- 
ting the effect of too early ignition is shown at D. The 
excessive back pressure from a io b is very evident. Too 
early ignition also gives the cylinder walls a chance to carry 
off an excessive amount of heat, owing to the slow speed of 
the piston at the end of the stroke. The diagram produced 
by such an engine lies inside that obtained when the ignition 
is properly timed, as shown by the dotted lines. The loss 
of work is shown by the difference in the areas of the two 
diagrams^ Fortunately, this is a condition promptly made 
evident by the behavior of the engine, and is soon remedied. 

60. Care must be taken that the diagrams produced by 
badly timed ignition are not confused with those produced 
by weaksned mixtures. Examples of the latter are shown in 
the indicator diagrams E and F, Fig. 21. In both of these 
diagrams, ignition takes place at a, but in diagram F the 
maximum pressure is not reached until the piston is at the 
middle of its stroke. In E, the maximum pressure occurs a 
trifle late, but it should be noted that the line ab is approxi- 
mately at right angles to the atmospheric line. The later 
occurrence of the maximum pressure is due, not to faulty 
timing of the ignition, but to the fact that flame propagation 
is slower in weak mixtures, and particularly when the com- 
pression pressure is low. The engine from which these 
diagrams were taken is governed by throttling both the gas 
and the air. 




51« Diasjam G^ Fig:. 21, indicates very clearly that tbe 
exhaust passages are obstructed. The point b should be qd 
the atmospheric line xy^ as shown in A at x. Instead, the 
line of the diagram does not reach xy until the piston 
returns to c. This may be due to a sluggish opening of the 
exhaust valve or to constricted exhaust passages. Some 
forms of exhaust mufflers will cause the production of such 
a diagram. 

Several of these defects may occasionally appear on one 
diagram. They are all more or less detrimental to the 
proper performance of the engine. The remedy will usually 
suggest itself in every case. Quite often, the remedy con- 
sists in the adjustment of the igniter mechanism or the 
proper setting of the valves. Sometimes, however, it will 
not be possible to remedy the defect except in a new design. 

When desired, the expansion curve may be compared with 
a theoretical curve by drawing a curve according to the law 
^ z;" == a constant, from a point on the expansion curve where 
the combustion is complete. The exponent n should be so 
chosen that the resulting curve will represent the average 
practice of engines of the type under consideration. In the 
absence of a more accurate value, the value of n for adiabatic 
expansion, namely, 1.405, is sometimes used. A comparison 
of the theoretical with the actual curve may reveal defects in 
the expansion curve that could not readily be detected with 
the eye. It must not, however, be supposed that the theo- 
retical and actual curves should entirely coincide. 

52. Fig. 22 shows a diagram taken with an indicator 
using a spring that is too weak, and is fitted with a safety 


stop, as explained in Art. 13, so that the higher pressures 
are not recorded. The sudden drop of the admission line at 
the point a shows that the admission valve opens too late. 
The horizontal line b^ at the top of the diagram, is caused 
by the stop limiting the vertical travel of the pencil when it 
rises to this point. The diagram cannot, therefore, be used 
lor determining the mean effective pressure. 


1. What is the mean effective pressure of an indicator diagram 
when the area is 1.88 square inches, the length of the diagram ii 
8.2 inches, and the scale of the spring is 90? 

Ans. 52.9 lb. per sq. in., nearly 

2. A gas engfine makes 5,800 explosions per hour, the piston dis- 
placement is .75 cubic foot, and the quantity of gas used per explosion 
is .1 cubic foot; what is the approximate number of cubic feet of air 
used per hour? Ans. 3,840 cu. ft. 

3. The diameter of an engine cylinder is 15 inches, and its stroke ia 

2A inches. The clearance is measured by the method of Art. 27. 

The weight of the bucket and water before filling the clearance space is 

62.5 pounds, and their weight after filling the space is 7.5 pounds. 

What is: (a) the piston displacement, in cubic feet? (b) the clearance, 

in cnbic feet? (r) the percentage of clearance? 

\{a) 2.15 cu. ft., nearly 
Ans.^ (bS .72 cu. ft. 

I \c) 33.5 per cent., nearly 

4. What is the brake horsepower of a gas engine running at 
226 revolutions per minute, when the pressure it exerts at the end of 
a 3-foot brake arm is 26 pounds? Ans. 3.34 H. P. 

5. Find the indicated horsepower of an engine from which the 
following results are obtained: mean effective pressure of indicator 
card, 96 pounds per square inch; length of stroke, 12 inches; diameter 
of piston, 9 inches; number of explosions per minute, 115. 

Ans. 21.28 H. P. 

6. How much heat is absorbed in work per hour in an engine of 
23.5 indicated horsepower? Ans. r>9,807 B. T. U. 

7. The exhaust gases of an engine weigh .07.') pound per cubic foot, 
the specific heat of the mixture is .225, the number of cubic feet of 
gas exhausted per hour is 45, the temperature of the room is 72°, and 
the temperature shown by the pyrometer is 375°; what is the quantity 
of heat exhausted per hour? Ans. 230 B. T. U., nearly 



8. What is the approximate horsepower of a two-cylinder, four- 
cycle, gas engine running at 200 revolutions per minute with a mean 
effective pressure of 75 pounds? The diameter of the cylinder is 
10 inches and the length of stroke 16 inches. Ans. 48 H. P. 


53. When the design of a gas engine has been decided 
on, and a number of engines built according to the desig^xii 
each one is tested in the shop of the makers before shipment 
to the purchaser. In such cases, it is not customary to 
make a very exact test, as this is unnecessary for the f^iir- 
pose of determining whether the performance of the engine 
comes up to the standard. The points to be determined by 
the test are: (1) whether the engine runs without undue -fxfc. 
tion or overheating, and without leakage at the piston or 
valves; (2) whether the valves and igniter are properly timed; 
and (3) whether the engine uses more than the guaranteed 
quantity of fuel per horsepower per hour, and whether it 
comes up to the guaranteed maximum horsepower. In the 
following articles is given an outline of the procedure adopted 
for tests of this kind by one of the largest manufacturers of 
gas engines. 

54. Before the engine reaches the testing stand, the 
piston has been fitted as accurately to the cylinder as pos- 
sible, so that there is little or no possibility of the gases 
blowing past the piston. It is, however, almost impossible 
to get a new piston so that it will run quite tightly for any 
considerable length of time without expanding. This makes 
it seize the cylinder in spots causing a knocking sound, which 
is due to ,the motion of the connecting-rod on the crank- 
pin and wristpin. Of course, this motion is very slight, and 
is only the necessary amount of freedom in the bearings; 
however, it makes quite a noise. As soon as this knock- 
ing develops, the en8:ine is stopped, and the piston taken 
out of the cylinder and carefully examined. The high spots, 
which are now very apparent, are carefully dressed do\Mi 
T/ith a smooth file. This is done very gradually, so as to 


avoid taking o£E too much, as to a certain extent the makers 
depend for tightness on the piston as well as on the rings. 
Generally, it is necessary to remove and dress down the 
piston three or four times in this manner before it reaches 
that condition where it can be operated continuously under 
full load. 

55. The indicator is used on every engine, but only for 
determining the adjustment of the valves and the timing of 
the ignition. When engines are being constantly tested and 
the number of indicators available is limited, it is found 
impracticable to keep the indicators in such condition that 
their results are trustworthy as regards the horsepower; 
hence, it is customary to determine the power by means of 
the Prony brake. 

56. When the engine is to be run with illuminating gas, 
the fuel consumption is determined by a meter that registers 
to hundredths of a cubic foot. The engine is generally tested 
at somewhat above the rated load, though still, perhaps, 
below its maximum load. The gas consumed per hundred 
charges is measiured and the number of charges* per 
minute coimted when the engine is running under the 
constant test load, and proper deduction made for charges 
missed. Engines built to use gasoline are tested ior 
fuel consumption by drawing the gasoline from a gradu- 
ated bottle; and, since the consumption is practically constant 
under constant load, it is found that a comparatively short 
test, using up 1 or 2 gallons of gasoline, according to the 
size of the engine, is sufficient. 

*The engine built by the company using this outline of tests la 
governed on the hit-and-miss principle. 



57. The efficiency of any engine is the ratio of the 
work actually performed to the work it is possible to obtain 
from the source from which the power is derived. The ratio 
of the work actually obtained from the motor to that con- 
tained in the source of supply is more often called the total 
efficiency; and, in the case of a gas engine, this may be 
obtained by dividing the work measured as the brake horse- 
power by the total work, or energy, in the gas used, for 
the same length of time. A convenient way to do this is to 
reduce the brake horsepower to equivalent British thermal 
units and divide the result by the British thermal units given 
up by the quantity of gas actually used in 1 minute. The 
total efficiency is seldom used in actual practice. There are, 
however, two other efficiencies that are frequently detennmed, 
namely, the thermal efficiency and the mechanical efficiency. 

68. Tliermal Efficiency. — The thermal efficiency 

is determined by dividing the heat absorbed by the engine 
by that supplied by the gas. The result is usually written 
as a percentage. In the theoretically perfect engine, the 
heat absorbed in work depends directly on the drop in 
the absolute temperature of the gas from the explosion 
to the exhaust temperature; and the total heat in the gas 
depends, in the same way, on the absolute temperature of 
the gas at explosion. For this reason, the formula for ther- 
mal efficiency is usually written: 

in which Et = thermal efficiency; 

Tx = absolute temperature of gas at explosion; 
7*, = absolute temperature of gas at exhaust. 
The thermal efficiency of any gas engine is the total 
efficiency of a perfect engine working between the same 


initial and final temperatures, because the perfect engine 
utilizes all the heat given up by the gas. Hence, the ther- 
mal efficiency is sometimes called the efHciauy of the perfect 

Example. — If the initial temperature of a gas at explosion is 
2,900'' F. and the exhaust temperature is 1,682*' F., what is the ther- 
mal efficiency of the engine? 

Solution.— T^ = 2,900° -|- 460° = 3,360°; r. = 1,682° -|- 460° 
s 2,142°. Substituting in the foregoing formula, the following equa- 
tion is obtained: 

Et = ^'^ i J — = .3625, or 36.25 percent. Ans. 

59, Mechanical Efficiency. — The delivered, or brake, 
horsepower (B. H. P.) is the horsepower delivered by the 
engine as measured by the dynamometer or Prony brake. 

The mechanical efficiency of an engine is the ratio of 
the brake horsepower to the indicated horsepower. It is 
usually expressed by the formula 

M. E. = ^' ^' ^' 
I. H. P. 

The difference between the indicated horsepower and the 

brake horsepower represents the power required to drive 

the engine, and is used to overcome the friction of the 

engine, so that, if the engine were running without load, 

the power required to run it would represent the friction 

load of the engine, or I. H. P. — B. H. P. Hence, it is easy 

to see that the lighter the load on an engine, the less the 

mechanical efficiency will be. 

Example.— (a) What is the friction load of an engine when the 
1. H. P. is 25 horsepower and the B. H. P. is 22 horsepower? [fi) What 
is the mechanical efficiency? 

Solution. — 
(a) Friction load = I. H. P. - B. H. P. - 25 - 22 - 3 H. P. Ans. 

(b) M. E. = -p-iT" p" ™ OR "■ ^ P®^ cent. Ans. 

Average mechanical efficiencies have been found to be 
about as given in Table II. An engine using a lean gas (that 
is, a gas of poor quality) and high compression will show 



a lower mechanical efficiency than one using: rich 
moderate compression. 



Size of Engine 



4 to 25 

25 to 500 

SCO upwards 

.74 to .80 
.79 to .81 
.81 to .86 

.63 to .70 
.64 to .66 
.63 to .70 


1. The temperature of a gas at explosion, in a gas engine, is 
2,740° P., and the temperature of the exhaust is 1,370° P.; what is the 
thermal efficiency? Ans. 42.81 per cent. 

2. The indicated horsepower of a gas engfine is 237, and the 
delivered horsepower is 215; what is its mechanical efficiency? 

Ans. 90.7+ per cent